Morphology and histology of the marine snail <italic>Haminoea vesicula</italic>

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Content M ORPHOLOGY AND HISTOLOGY O F TH E M ARINE SNAIL HAM INOEA VESICULA by M ay M ei-Y in g C hen A T h e s is P r e s e n te d to the FA C U LT Y O F TH E GRADUATE SCHOOL UNIVERSITY O F SO U TH ERN CA LIFO RN IA In P a r t i a l F u lfillm e n t of the R e q u ire m e n ts fo r the D e g re e M A STER O F SCIEN CE (Z oology) J u n e 1959 UMI Number: EP67229 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMI Dissortation Publishing UMI EP67229 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 UNIVERSITY O F SOU TH ERN CALIFORNIA G R A D U A T E S C H O O L U N IV E R S IT Y PA R K L O S A N G E L E S 7 . C A L IF O R N IA Z This thesisj written by .................. M ax.M e.ir.Y .lng....C .ben.................. * I under the direction of h.QX...Thesis Committee, and approved by all its members, has been pre- HI ^ ^ sented to and accepted by the Graduate School, in partial fulfillment of requirements for the degree of ........ Mâs.t.er. . . Q f . . . S . Q . i ^ n e . Q . ........ Dean Date June,....19.5.9.. THESIS COMMITTEJ Chairman ~ T ~'~T ~ ^ c L v j l w - T A B L E O F CO N TEN TS SEC TIO N PA G E I. I N T R O D U C T I O N ............................................................................ 1 A ck n o w led g m en ts .................................................................. 2 II. M A TERIA LS AND M ETHODS .............................................. 4 III. OBSERVA TION AND DISCUSSION .................................... 8 E x te r n a l M o r p h o l o g y ............................................................. 8 C ep h a lic r e g i o n .................................................................. 9 M antle and V is c e r a l M a s s ......................................... 11 C y an o p h ilo u s g l a n d s ........................................................ 14 T he f o o t ................................................................................. 15 D ig e stiv e S y ste m .................................................................. 16 D ig e stiv e t r a c t .................................................. 17 M outh and the b u c c a l m a s s ............................... 17 E so p h a g u s and a n te r io r c r o p ............................... 21 G iz z a rd and p o s te r io r c r o p ............................... 22 S t o m a c h ............................................................................ 23 In te stin e and r e c t u m .............................................. 24 D ig e stiv e g l a n d s .................................................................. 27 S a liv a ry g l a n d ............................................................. 27 L i v e r ................................................................................. 29 C ir c u la to ry S y s t e m .................................................................. 30 ii I l l SECTIO N PA G E R e s p ir a to r y S y ste m ............................................................. 32 E x c r e to r y S y s t e m .................................................................. 33 N e rv o u s S y ste m and S ense O r g a n s ............................... 34 N e rv o u s s y s t e m .................................................................. 34 C e r e b r a l g an g lia and n e r v e s ............................... 35 P e d a l g an g lia and n e r v e s .................................... 37 P l e u r a l g an g lia and n e r v e s ............................... 38 S ense o r g a n s ....................................................................... 40 E y e s ................................................................................. 40 O s p h r a d i u m .................................................................. 41 O to c y sts ( o r S t a t o c y s t s ) ......................................... 42 R h i n o p h o r e s .................................................................. 42 R e p ro d u ctiv e S y s t e m ............................................................. 43 A c c e s s o r y g l a n d s ............................................................. 48 S e m in a l r e c e p t a c l e ................................................... 48 A lb u m en g l a n d ............................................................. 49 F e m a le m u c o u s g l a n d .............................................. 50 S p e r m a t h e c a .................................................................. 51 M ale o rg a n s ....................................................................... 51 P r o s t a t e g l a n d ............................................................. 51 P e n is and p en ial s h e a t h ......................................... 52 IV. S U M M A R Y ................................................................................................ 55 IV SECTIO N PA G E A P P E N D I X E S ........................................................................................................... 60 A PPE N D IX A. LIST O F ABBREVIATIONS . . . . 61 A P P E N D IX B. P L A T E S ...................................................... 67 L IT E R A T U R E C ITED ....................................................................................... 102 LIST O F MAPS MAP PA G E I. P a c ific C o a s t of C a lifo rn ia , fro m M alaga C ove to San P e d r o ..................................................................................................... 5 LIST O F P L A T E S P L A T E PA G E I. S H E L L AND SNAIL ........................................................................ 68 II. P A L L IA L C O M P L E X AND CIRC U LA TO R Y SY STEM . 70 III. SECTIONS O F C E P H A L IC AND P A L L IA L REGIONS . 72 IV. SECTIONS O F M A N TLE SKIRT AND P E D A L TISSUE . 74 V. D IG ESTIV E S Y S T E M .............................................................. 76 VI. B U C C A L C O M P L E X .............................................................. 78 VII. SECTIONS O F B U C C A L A REA AND R ADULA SAC . . 80 VIII. G IZZA RD AND RADULA T E E T H .......................................... 82 IX. SECTIONS O F G IZZA RD D IV ER TIC U L U M AND L I V E R ................................................................................. 84 X. SECTIONS O F D IG ESTIV E ORGANS, GLAND, AND R H I N O P H O R E ............................... 86 X I. SECTIONS O F H E A R T AND K I D N E Y ........................... 88 X II. NERVOUS SYSTEM ........................................................................ 90 XIII. SECTIONS O F EY E AND O T O C Y S T ........................... 92 XIV. R E PR O D U C T IV E S Y S T E M ............................................... 94 XV. SECTIONS O F H E R M A PH R O D ITE GLAND AND F E M A L E MUCOUS G L A N D .................................... 96 XVI. SECTIONS O F G E N IT A L ACCESSORY GLANDS AND H E R M A PH R O D ITE D U C T .......................... 98 vi v i l P L A T E PA G E XVII. SECTIO N S OF CA ECU M AND P R O S T A T E GLAND . . 100 I. INTRODUCTION H a m in o e a v e s ic u la Gould is a m a rin e g a s tro p o d of the s u b - c la s s O p isth o b ra n c h ia . T h is s u b - c la s s is divided into two o r d e r s , T e c ti- b ra n c h ia , including f o rm s w ith s h e ll and c te n id iu m , su ch as H a m in o e a ; and N u d ib ra n ch ia, f o rm s w ithout s h e ll and tru e c te n id iu m . A c c o rd in g to G ra y (1847), L e a c h m a d e th e o r ig in a l d e sig n a tio n of th e genus H a m in a e a in 1818. T u rto n and K in g sto n (1830) u sed the sp e llin g H a m in o e a . G ra y (1847) n am ed it H a m in e a , but the nam e H am in o ea is m o re w idely a c c e p te d . T he follow ing is I r e d a le ’s (1914) s h o rt note r e g a rd in g th e g e n e ric n am e: ' ' H a m in e a is g e n e ra lly quoted a s of the P r o c . Z ool. Soc., 1847 (N o v em b er, 1847), bu t I had noted th a t it a p p e a re d e a r l i e r in the Ann. M ag. N at. H is t., Vol. XX, p. 268, O c to b e r 1, 1847, w h e re it w a s s p e lt H a m in a e a . I now tr a c e it b ack to 1830, as th is is in clu d ed , th u s: H a m in o e a . S h ell th in , so m ew h at g lo b u la r, w ith o u t s p ir e ; a p e r tu r e n a rro w , as long a s the s h e ll. In c lu d e s B u lla h y d a tis . We m u s t th e r e fo r e q u o te .” G ould (1855) d e s c rib e d the s p e c ie s , H a m in o e a v e s ic u la . Since th en the lit e r a t u r e show s m u ch d is a g r e e m e n t as to the stan d in g of H. v e s ic u la below the o r d e r le v e l. F i s c h e r (1883) and C ooke (1927) c o n s id e re d H a m in o e a a s a s u b g en u s u n d e r the genus B u lla in th e fa m ily B uIIidae. A d a m s and A d am s (1858) a lso p laced it in th is fa m ily . T ry o n (1893), S ch ep m an (1913), 1 O ldroyd (1927), Sm ith (1945), and K een and P e a r s o n (1952), a ll c o n s id e re d it a m e m b e r of the fa m ily A k e rid a e . P r a t t (1935), and J o h n so n and Snook (1935) p la c e d it in the fa m ily A k e ra tid a e u n d e r the s u b - o r d e r C e p h a la sp id e a of the o r d e r T e c tib r a n c h ia w hich w a s s u b d iv id ed into C e p h a la sp id e a , A nas p id ea and N o ta sp id e a by F i s c h e r (1883). T h ie le (1931) and A bbott (1954) p laced it in th e fa m ily A ty d ae, w hich a p p e a r s to be m o s t a c c e p ta b le in line w ith re c e n t tax o n o m y . The co m m o n n a m e fo r H. v e s ic u la is the " w h ite b u b b le .” Its ra n g e is fro m A la s k a to the G ulf of C a lifo rn ia (A bbott 1954). U su a lly d u rin g the e g g -la y in g s e a s o n in the e a r ly s u m m e r , H a m in o e a m ig ra te fro m the d e e p w a te r into sh allo w w a te r . T h ey a r e found u n d e r and o c c a s io n a lly upon the e e l - g r a s s and alg a e in tide p o o ls. E g g s a re d e p o site d w ith in a so ft, rib b o n -lik e r o ll of g e la tin w hich a d h e r e s to the e e l - g r a s s . T h e re is little in fo rm a tio n on the m o rp h o lo g y and h isto lo g y of H. v e s ic u la . T he p r e s e n t w o rk w as u n d e rta k e n to in c r e a s e o u r k n o w led g e o f th e a n a to m y and the h is to lo g ic a l e le m e n ts of th is a n im a l. A ck n o w led g m en ts T he w r i t e r ta k e s th is o p p o rtu n ity to e x p r e s s h e r d eep a p p r e c i a tio n to D r . N o rm a n T . M attox a t w hose su g g e stio n and u n d e r w hose d ire c tio n th is w o rk w as c a r r i e d out. M any g ra te fu l thanks a r e due a ls o to the m e m b e r s of the g u id an ce c o m m itte e — D r. N o rm a n T . M attox, D r. W a lte r E , M a rtin , D r . T . T . C h e n — fo r th e ir tim e , in te r e s t, and c o n trib u tio n s . T h e w r i te r w is h e s a ls o to th an k D r . J e n s W. K nudsen fo r h is h e lp in c o lle c tio n , M r. D onald B . B rig h t fo r h is a s s is ta n c e in th e p h o to m ic ro g ra p h ic tech n iq u e e m p lo y e d , and m an y frie n d s fo r th e ir v a lu a b le help and s u g g e stio n s. II. M A TERIA LS AND M ETHODS T he s p e c im e n s upon w hich th e follow ing study w as m a d e w e re c o lle c te d fro m tid e p o o ls in tw o p la c e s — L unada B ay, P a lo s V e r d e s , C a lifo rn ia , on M ay, 1957; and P o in t F e r m in , San P e d r o , C a lifo rn ia , on N o v e m b e r 1957 (M ap 1). D u rin g low tide the s n a ils w e re u s u a lly found in the tid e pools w h e re e e l - g r a s s and a lg a e w e re ab u n d an t. It w as d ifficu lt to s e e th e m ow ing to th e ir c o lo r b ein g so s i m i l a r to the s u b s tr a te in w hich th e y h id e . H o w ev er, th e b rig h t yellow egg rib b o n s alw ay s in d ic a ted the p r e s e n c e of th e s e a n im a ls . O v e r 300 in d iv id u a ls w e re c o lle c te d in th is stu d y . O w ing to the la rg e opening of th e s h e ll, the so ft p a r ts of the a n im a ls w e r e e a s ily re m o v e d u n in ju re d by s e p a ra tin g the c o lu m e lla m u s c le f ro m the s h e ll and allow ing th e v i s c e r a l m a s s to be g en tly tw iste d out. F o r th e p u rp o se of a n a to m ic a l stu d y , re la x a tio n of the soft p a r ts th ro u g h a n e s th e tiz a tio n w a s m ad e by one o r the o th e r of the tw o follow ing m e th o d s: 1. S m a ll am o u n ts of m a g n e s iu m su lfa te w e re added to a fin g e r bow l co n tain in g a p p ro x im a te ly 100 m l. of s e a w a te r in w hich ten to fifte e n s n a ils w e re p la c e d . At ab o u t o n e -h o u r in te rv a ls a su ffic ie n t am o u n t (ab o u t one tea sp o o n fu l) of m a g n e s iu m su lfa te w as added fo r a p e rio d of six to eig h t h o u rs . O v e rd o s e s of m a g n e s iu m su lfa te k ille d th e a n im a ls . 4 M AP I P a c if ic C o a s t of C a lifo rn ia , fro m M ala g a C ove to San P e d r o . T he s p e c im e n s w e re c o lle c te d fro m P o in t F e r m in , San P e d ro ; and L u n ad a B ay, P a lo s V e rd e s . to < / > u. 2. S p e c im e n s k ep t in r e f r ig e r a te d s e a w a te r o v e rn ig h t w e re c o m p le te ly re la x e d . T he s p e c im e n s w e re k illed by p lacin g th e m in the f r e e z e r fo r about 24 h o u r s . T he seco n d m ethod gave b e tte r r e s u lts . L iving and p r e s e r v e d s n a ils w e re d is s e c te d . In the f o r m e r , the a n im a ls w e re re la x e d w ith m a g n e s iu m su lfa te o r by fre e z in g and th e n d is s e c te d in s e a w a te r . F o r the la tte r , s n a ils w e re k illed in 70 p e r cen t alco h o l; and p r e s e r v e d in a m ix tu re of th re e p a r ts of 70 p e r c e n t alco h o l and one p a r t of g ly c e rin e o r 5 p e r c en t fo rm a lin so lu tio n . T he s p e c im e n s u s e d fo r h isto lo g ic a l stu d y w e r e fixed w ith e ith e r H e id e n h a in 's fix ativ e (100 m l. of s a tu r a te d aqueous m e r c u r ic c h lo rid e w ith 2 g r a m s tric h lo r o a c e tic a c id and 1 m l. a c e tic a c id ) o r B o u in ’s fluid (75 p e r c e n t s a tu r a te d a q u e o u s p ic r ic acid w ith 25 p e r c e n t n e u tr a l fo rm a ld e h y d e and 5 p e r c e n t g la c ia l a c e tic acid w hich is added im m e d ia te ly b e fo re u sin g ). F o r s e c tio n in g the g iz z a rd p la te s o r o th e r h a rd p a r ts of th e s n a il, H e id e n h a in ’s “ SUSA** w as the m o s t s a tis f a c to r y fix a tiv e . S e r ia l s e c tio n s w e re cu t fro m 5 to 10 m ic ro n s th ick and w e re s ta in e d w ith G alig h er* s a lu m H ae m a to x y lin . A 0.5 p e r c e n t so lu tio n of T r io s in in 95 p e r c e n t e th y l a lco h o l at pH 5.4 to 5.6 w as u se d a s a c y to p la sm ic c o u n te r s ta in . F o r pH a d ju stm e n t, 4 m l. of 0.1 h y d ro c h lo ric acid w as added in 100 m l. of the dye so lu tio n . In 12 m l. of s ta n d a rd h a e m a to x y lin 88 m l. of s a tu r a te d aq u eo u s a lu m in iu m am m o n iu m su lfa te w as added a s th e m o rd a n t. T h e s ta n d a rd p r o g r e s siv e sta in in g p ro c e d u re w a s em p lo y ed . III. O BSERVA TION AND DISCUSSION A ll m e a s u r e m e n ts given in th is p a p e r a r e th o se ta k e n fro m s n a ils 26 m m in length, the a v e ra g e s iz e of the s p e c im e n s c o lle c te d . E x te r n a l M orphology T h e living s n a il is d a r k g r a y is h b ro w n w ith b la c k and w hite s p o ts . T h e p a r t c o v e re d by s h e ll is a d a r k e r b ro w n , b e a rin g b rig h t o ra n g e and w hite s tip p le s and i r r e g u l a r g ra y is h fle c k s. T h e c o lo ra tio n of the s k in is due to p ig m en t g r a n u le s , w hich a r e so lu b le in alco h o l. T h e a n im a l u s u a lly im ita te s the c o lo r of its e n v iro n m e n t, upon w hich it is found. T he body is so ft and is s lim y . T he a v e ra g e s n a il length is 26 m m ; the g r e a te s t w idth is 12 m m . T h e se a v e r a g e s a r e b a s e d on m e a s u r e m e n ts of 100 s n a ils ( F ig u r e 3). T h e s h e ll is oval, f ra g ile , tra n s lu c e n t, and c o v e re d w ith a y e llo w ish p e r io s tr a c u m . It v a r ie s fro m w h itish o r iv o ry to a pale h o rn y b ro w n , s o m e tim e s ev en lig h t la v e n d e r and u s u a lly sp e c k le d w ith i r r e g u l a r r u s ty p a tc h e s . Its s u rf a c e is s c u lp tu re d w ith in d istin c t g r o w th -lin e s . T he s h e ll alw ay s f o r m s one and a h a lf d e x tr a l w h o rls. T he ap ex is tru n c a te w ith a v e r y s m a ll sun k en s p ir e . T h e m a rg in of th e in n e r lip is re fle x , the o u te r p o rtio n thin and a rc u a te and ex ten d in g o v e r th e apex. T he c o lu m e lla is d e e p ly co n cav e, its r e fle c te d b o r d e r is co n flu en t w ith the r e fle c te d m a r g in of the in n e r lip ( F ig u r e s 1 and 2). 8 9 T he a p e r tu r e of the s h e ll e x te n d s the e n tire length of the rig h t sid e and is p ro lo n g e d beyond the apex of the s h e ll. T h e a n te r io r d o r s a l b o r d e r of the s h e ll is a tta c h e d to the v i s c e r a l m a s s by the c o lu m e lla r m u sc le w hich o rig in a te s at the s h e ll and o ffe rs the only point of a tta c h m e n t b etw een the v i s c e r a l m a s s and th e s h e ll. T h e s h e ll is not la r g e enough to c o m p le te ly s h e lte r the c o n tra c te d body. T h e body m a y be div id ed into th re e re g io n s: c e p h a lic , v i s c e r a l m a s s , and foot. T h e body ca v ity o r h e m o c o e le is s e p a ra te d into an a n te r io r p o rtio n in the c e p h a lic re g io n , and a p o s te r io r p o rtio n in the v i s c e r a l m a s s re g io n , by a sh e a th of co n n ectiv e tis s u e , the d ia p h ra g m . C e p h a lic R egion T he a n te r io r re g io n of the body c o n s is ts of cep h alic sh ie ld o r head and n ec k . T he a n te r io r p a r t of th e sh ie ld te r m in a te s b ro a d ly , and the p o s te r io r end ex ten d s b a c k w a rd to o v e rla p the s h o rt n eck re g io n and the a n te r io r b o r d e r of the s h e ll. T he head is c o v e re d by a p ig m e n te d e p id e r m is c o n s is tin g of c o lu m n a r c e lls w ith b a s a l, oval n u c le i. M ost of the e p ith e liu m is ev e n ly c o v e re d w ith c ilia . T he h ead b e a r s the m o u th , a p a ir of p a lp s, a p a ir of a u ric u la te te n ta c le s , a p a ir of e y e s , a p a ir of rh in o p h o re s and the m a le c o p u la- to ry o rg a n . T h e m o u th is a v e r tic a l s lit lying b etw een the p alp s in the g ro o v e b etw een the c e p h a lic sh ie ld and the foot; th is groove ru n s b a c k 10 into g ro o v e s b etw een p a ra p o d ia and the v i s c e r a l m a s s . On e a ch side of the a n t e r i o r h ead re g io n is an a u ric u la te te n ta c le , the ta c tile o rg a n , w hich is no t ev id e n t u n le s s the a n im a l is m oving. N e a r the in n e r b a s e s of the s h o r t a u ric u la te te n ta c le s lie the p a ire d e y e s , e a c h of w hich is a b la c k sp o t s u rro u n d e d by a c i r c u l a r p atch of u n p ig m en ted e p id e r m is . T h e y e llo w ish rh in o p h o re s a r e lo cated on e a c h sid e of the body along the a n t e r i o r p a r t of the g ro o v e s b etw een the c e p h a lic sh ield and the foot. T h e y fu n ctio n a s o lfa c to ry o rg a n s . T h e rh in o p h o re s a r e co n tin u o u s w ith the p alp s w hich a r i s e fro m the a n te r io r end of eac h of th e rh in o p h o re s as a fold on e a c h sid e of the m outh in the g ro o v e b e tw een the h ead and th e foot. T he m a le opening th ro u g h w hich the p en is is p r o tr a c te d is in the rig h t g ro o v e b etw een the h ead and the foot u n d e r the b a s e of the rig h t te n ta c le . F r o m the m a le opening ru n s a sh allo w open g ro o v e, the s e m in a l g ro o v e , w hose l a t e r a l w a lls a r e tw o p ro je c tio n s fro m the body w a ll along the g ro o v e b etw een the v is c e r a l m a s s and the rig h t p a ra p o d iu m . T he s e m in a l g ro o v e ru n s p o s te ria d into the g e n ita l opening. The c a v ity in the c e p h a lic re g io n is the a n t e r i o r h e m o c o e le lined by a n e tw o rk of m u s c le f ib e r s . It c o n s is ts of the b u c c a l m a s s , e so p h a g u s and g iz z a rd lying along the m e d ia n ax is; a p a ir of s a liv a r y glan d s along e ith e r sid e of the e so p h ag u s; the n e rv e rin g and ganglia; and the m a le c o p u la to ry o rg a n w ith the y e llo w ish p r o s t r a t e gland 11 p laced on the left and the p e n ia l s h e a th a c r o s s the ro o f and to w a rd the rig h t. T he s h o r t b ro a d n eck b etw een the v i s c e r a l and the c e p h alic sh ie ld is c o m p le te ly c o n c ea le d by the p o s te r io r flap of the l a tte r . M antle and V is c e r a l M a ss (F ig u re 5) T h e v i s c e r a l m a s s is c o v e re d by the m a n tle w hich is fixed on the left sid e but f re e on th e rig h t sid e of the a n im a l. T he m a n tle is u n ifo rm ly th in d o r s a lly , but b e c o m e s th ick and fle sh y to w ard its a n te r io r and rig h t edge to fo rm th e m a n tle s k ir t w hich is d o tted w ith w hite s p o ts . A n a r ro w fu rro w , the m a n tle g ro o v e a s in C y lin d ro b u lla (M a rc u s, 1956), ru n s along the edge of th e w hole length of the m a n tle s k ir t th u s s e p a ra tin g two r id g e s along e ith e r sid e of the m a n tle g ro o v e , the m a r g in a l fold o u tsid e of the m a n tle g ro o v e and th e she 11-fo rm in g gland cu sh io n in s id e . The p o s te r io r p a r t of the in f e r io r b o r d e r of the m a n tle is tu rn e d o v e r the s h e ll fo rm in g a th ick e x p an sio n , “ e x p an sio n epicochleaire** ( P e r r i e r and F is c h e r , 1911) of the in fr a p a llia l lobe ( F ig u re 5). T h e c o v e rin g of the m a n tle is s im p le cu b o id al e p ith e liu m , e a c h c e ll of w hich h a s a round o r slig h tly elo n g a ted n u c le u s. B en e ath th is is a la y e r of co n n ec tiv e tis s u e in te rla c in g w ith m u sc le f ib e rs and blood s p a c e s . T h e e p ith e liu m of the m a n tle s k ir t show s a tr a n s itio n fro m the cu b o id al c e lls to low c o lu m n a r c e lls . T h e s h e ll fo rm in g gland c u sh io n is fo rm e d by an e p ith e liu m c o n s is tin g of ta ll c e lls , w hich is 12 d is tin c tly s e t off fro m n eig h b o rin g e p ith e liu m . T he o v al o r elo n g ated n u c le u s of the ta ll c e ll is p la c e d in the d is ta l p a r t of the d a rk ly s ta in ing, g ra n u la te d c y to p la sm . I n te r s p e r s e d w ith th e se c e lls a r e the fla s k -lik e gland c e lls , the b o d ies of w hich re a c h a h eig h t n e a r ly o n e- th ird th a t of the e p ith e liu m . T h e se gland c e lls have b a s a l s p h e r ic a l n u c le i c o n tain in g g ra n u le s . T he m a n tle s k ir t c o n s is ts of th re e ty p e s of gland c e lls . T h e f i r s t type (F ig u re 10) and the m o s t c o n sp ic u o u s, h a s a la r g e , c e n tr a lly lo ca te d , round n u c le u s and c y to p la sm w ith s e c r e tio n s c o n c e n tra te d in the c e n te r , th u s fo rm in g a c i r c u l a r sp a c e b etw een the c e ll in c lu sio n s and th e c e ll m e m b ra n e . T h e se c e lls a r e s e t in the p a llia i tis s u e and s u rro u n d e d by a r e tic u lu m of m u s c le f ib e r s . T he o th e r tw o ty p e s of gland c e lls a r e the light p u rp le and pale pink i n f r a - e p ith e lia l gland c e lls lying n e a r the m a n tle edge and the m a n tle fold re g io n ; e a c h of th e m h a s a s m a ll n u c le u s , u su a lly n e a r the edge of the c e ll. B etw een the body and the m a n tle is a c r e s c e n t- s h a p e d s p a c e , the p a llia i o r m a n tle cav ity , w hose a p e r tu r e ex ten d s fro m the left p a r a podium and o v e r its w hole length on the rig h t sid e c o rre s p o n d in g to the e x te n sio n of the s h e ll a p e r tu r e . T he p a llia i ca v ity c o n ta in s the sin g le p in n ated c te n id iu m lying a c r o s s th e ro o f of the ca v ity w ith o n e - h a lf of it a tta c h e d to the k id n ey and the o th e r h a lf hanging f re e ly fro m its d o r s a l a tta c h m e n t in a h a lf c ir c le into the m a n tle ca v ity . T h e o s p h r a d iu m is s itu a te d a t the a n te r io r a tta c h m e n t of the c te n id iu m to the body 13 w all. T he k idney is lo c a te d in the ro o f of the p a llia i c a v ity , but its tin y r e n a l p o re op en s below the b o r d e r of th e c te n id iu m a n te r io r to the r e c tu m . T h e an u s is situ a te d in the fu rro w b e tw e e n the ro o f and flo o r in the in n e r m o s t p a r t of the p a llia i cav ity . A t th e rig h t a n te r io r lim it of the m a n tle a p e r tu r e in the gro o v e b etw een the v i s c e r a l m a s s and the r ig h t p a ra p o d iu m op en s th e g e n ita l p o re , fro m w hich the s e m in a l g ro o v e ru n s fo rw a rd to the m a le opening. D o r s a l and v e n tr a l to the an u s, on the ro o f and flo o r of the p a llia i ca v ity , a r e two v o lu m in o u s m u c o u s p ro d u c in g g la n d s, th e cyan o p h ilo u s g lan d s (M a rc u s , 1956), e n c irc le d by c ilia te d b an d s w hich w ill be d e s c rib e d la te r . T h e v e n tr a l c ilia te d band lie s on a c i r c u l a r rid g e w hich w ith its in te rv e n in g tis s u e p r o je c ts fro m the m a n tle flo o r and m ig h t be c o n s id e re d a s a p a llia i c a e c u m . T he v i s c e r a l m a s s , co ate d by a thin t r a n s p a r e n t la m in a te d m u s c u la r tis s u e , o c c u p ie s m o s t of th e p o s te r io r o r v i s c e r a l h e m o c o ele w hich is s e p a r a te d fro m the a n te r io r by the th in “ diaphragm .** T h e v i s c e r a l m a s s c o n ta in s the d ig e stiv e o rg a n s , i . e . , the v o lu m in o u s liv e r, the s to m a c h and th e in te s tin e , and the re p ro d u c tiv e o rg a n w ith its a c c e s s o r y g la n d s. T h e p o s te r io r p o rtio n of the v i s c e r a l m a s s e x ten d s beyond the p o s te r io r lim it of the body c a v ity and is w ra p p e d by a th ic k ex p an sio n of the in fra p a llia l lobe. T he p e r ic a r d ia l c a v ity lie s o v e r the a n t e r io r re g io n of the v i s c e r a l h e m o c o e le . 14 C y an o p h ilo u s G lan d s B eh in d the c te n id iu m , the c y an o p h ilo u s g lan d s lie on the ro o f and flo o r of the p a llia i c a v ity and extend fro m the p o s te r io r lim it of the m a n tle s lit to about the le v e l of the p o s te r io r end of the g ill ( F ig u re 42). T h ey a r e la r g e , oval, opaque, g la n d u la r s tr u c t u r e s , about 3.5 m m by 3 m m , s u rro u n d e d by s e m i c i r c u l a r , b ro a d , c ilia te d b a n d s . T he gland is lined th ro u g h o u t w ith la rg e m u c o u s s e c r e tin g c e lls and s le n d e r e p ith e lia l c e lls ( F ig u re 9). T he e p ith e liu m of the c ilia te d band c o n s is t s of c o lu m n a r c e lls w ith b a s a l o r c e n tr a l e lo n g ated n u c le i. T h is c o lu m n a r c ilia te d e p ith e liu m is co n tin u o u s on both s id e s w ith g la n d u la r e p ith e liu m w hich f o r m s a g la n d u la r band alo n g each sid e of the rid g e . T he e p ith e liu m c o n s is ts of th re e ty p e s of c e lls , the pink a c id o p h ilo u s g la n d u la r c e lls w ith la rg e b a s a l o r c e n tr a l s p h e ric a l n u cle i, the blue b a so p h ilo u s c e lls w ith la rg e b a s a l s p h e r ic a l n u c le i and the c o lu m n a r e p ith e lia l c e lls w edged b etw een the g la n d u la r c e lls and h av in g e lo n g a te d n u c le i in the d is ta l end. T he in n e r b an d , th a t lie s b etw een the c ilia te d band and the cy an o p h ilo u s gland, sh o w s a g ra d u a l tra n s itio n fro m the gland c e lls to the m u c o u s cy an o p h ilo u s c e lls . B en eath the e p ith e liu m of the c ilia te d rid g e and the p a llia i c a e c u m lie la rg e blood s p a c e s c r i s s - c r o s s e d by s le n d e r s tr a n d s of m u s c le (F ig u re 55). A m o e b o c y te s a r e a ls o found h e r e . T he m o s t c o n sp ic u o u s p a llia i gland c e lls w ith c e n tr a l c o n c e n tra te d c y to p la sm found in the tis s u e of the m a n tle s k ir t a r e a ls o p r e s e n t in the tis s u e u n d e rly in g the s u rfa c e e p ith e lia . 15 It is thought th a t the c ilia r y c u r r e n ts w ith th e help of the m u c o u s p ro d u c e d by the cy an o p h ilo u s g lan d s d is c h a rg e the fa e c e s fro m the p a llia i ca v ity . T he F o o t T he foot is an elo n g a te d , fla tte n e d , m u s c u la r s tr u c tu r e w hich o c c u p ie s the v e n tr a l s u rf a c e of the a n im a l. It e x te n d s to the a n te r io r lim it of the h ead , b e in g s e p a r a te d fro m it by a t r a n s v e r s e g ro o v e. P o s t e r i o r l y , its s tr a ig h t hind b o r d e r c o n n e c ts the p o s te r io r en d s of the p a ra p o d ia . T h e p a ra p o d ia ( F ig u re 5) a r e a p a ir of tr ia n g u la r la te r a l e x p a n sio n s of the foot a r is in g u p w ard to c o v e r the g r e a t e r p a r t of s h e ll. T h e a p e x e s of the p a ra p o d ia re a c h to w h e re the flap of the c e p h a lic sh ie ld m e e ts the v i s c e r a l m a s s . T he in fr a p a llia l lobe p r o je c ts beyond the p o s te r i o r b o r d e r of the foot a s a “ tail** p o s te r io r to the v i s c e r a l m a s s , and its th ick e x p a n sio n , “ e x p a n sio n epicochleaire** w ra p s the hind end of th e s h e ll. T he p ed al e p ith e liu m c o n s is ts of c o lu m n a r c e lls w ith b a s a l, oval, o r slig h tly e lo n g ate d n u c le i. The p ed al so le is c ilia te d th ro u g h o u t (F ig u re 11). T h e p o rtio n of the foot b e n ea th the e p id e r m a l la y e r , is c o m p o se d of a n e tw o rk of co n n ectiv e tis s u e w ith ab u n d an t la c u n a e o r blood s p a c e s , and n u m e ro u s m u sc le f ib e r s . In te rn a lly , the m u s c le s a r e a r ra n g e d at ra n d o m a s the b o u n d ary of th e body c a v ity (h e m o c o e le). T h e re a r e two ty p e s of p ed al gland: the d iffu se and the 16 c o n c e n tra te d . T h e f o r m e r a r e e n la rg e d f la s k - lik e c e lls w ith s m a ll n u c le i found in the lo o se tis s u e lying b en eath th e c ilia te d e p ith e liu m . T he neck of the fla sk is p ro lo n g e d into a d u ct lea d in g to w a rd th e body s u rf a c e fo r the d is c h a rg e of th e s e c r e tio n s ( F ig u re 11). T h e s e glands a r e d is trib u te d o v e r th e w hole s u rf a c e of the foot, and s i m i l a r to th o se w hich o c c u r in m o s t p a r ts of th e p e r ip h e r a l p o rtio n of the body. The o th e r type g lan d s a r e c o n c e n tra te d in th re e re g io n s of th e foot: the a n t e r io r p e d a l gland in the a n te r io r end of the foot, the s u p r a - p e d a l gland in th e g ro o v e b e tw e e n th e h e a d re g io n and the foot, and the p o s te r io r p ed al g land in the p o s te r io r end of th e foot. T h e gland c e lls r e s e m b le the d iffu se c e lls , bu t a r e c lo s e ly p ack ed to g e th e r. T h e foot h as both fu n ctio n s of a tta c h m e n t and lo c o m o tio n . It is s ta te d by v a rio u s o b s e r v e r s ( P a r k e r , 1911, and o th e r s ) th a t d u rin g c re e p in g the p e d a l m u s c le e x h ib its a s e r i e s of slow w a v e -lik e m o v e m e n ts . D ig e s tiv e S y ste m T h e d ig e stiv e s y s te m of H. v e s ic u la c o n s is ts of tw o p a r ts : the d ig e stiv e t r a c t , and the d ig e s tiv e g la n d s. T he m o u th , b u c c a l m a s s (b e a rin g a p a ir of l a t e r a l ja w s , r a d u la , and o d o n to p h o re ), e so p h a g u s, g iz z a r d , s to m a c h , in te s tin e , and th e anus c o m p o se the f o r m e r ; two s a liv a r y g lan d s and a v o lu m in o u s liv e r co m p o se the l a t t e r ( F ig u re 12). T he d ig e stiv e s y s te m o c c u p ie s th e m a in p o rtio n of the body cav ity ; the 17 b u c c a l m a s s , th e e s o p h a g u s, and the g iz z a rd in the c e p h a lic h e m o - c o e le , the liv e r and the r e m a in d e r of the d ig e stiv e t r a c t in th e v i s c e r a l h e m o c o e le . D ig e stiv e T r a c t M outh and th e b u c c a l m a s s . T he m o u th o p en s b etw een the s e n s o r y p alp s in the g ro o v e b e tw e e n the foot and the c e p h a lic sh ie ld . It is s u rro u n d e d by an o r a l s p h in c te r m u s c le . T he la b ia l w a ll is folded into lo n g itu d in al rid g e s w hich allow a c o n s id e ra b le e x p a n sio n of the m o u th . T h is la b ia l re g io n , lined by a c u tic u la te d c o lu m n a r e p i th e liu m w ith b a s a l e lo n g ated n u c le i, en d s w ith a c i r c u l a r g ro o v e p o s te r io r ly , w hich s e p a r a te s th is re g io n fro m th e b u c c a l w a ll. T he m outh le a d s into the b u c c a l cav ity . T he b u c c a l m a s s is a p e a r - s h a p e d , hig h ly m u s c u la r o rg a n w hich is h e ld in p la ce by m u s c le b an d s a tta c h e d to the b u c c a l m a s s and ra d ia tin g out to the body w a ll ( F ig u r e s 14, 15, and 16). T he b u c c a l c a v ity , e x c e p t fo r the p o s te r io r p a r t of the d o r s o - p h a ry n g e a l c a n a l is lined th ro u g h o u t by a c u tic u la te d e p ith e liu m w hich c o n s is ts of c o lu m n a r e p ith e lia l c e lls w ith b a s a l o v al n u c le i and p ig m e n ted g r a n u la r c y to p la sm above th e n u c le i. In th e re g io n of the ja w s the e p ith e liu m is ab u n d an tly i n te r s p e r s e d w ith m u c o u s c e lls w hich push th e n u c le i of the e p ith e lia l c e lls e ith e r fo rw a rd o r b a c k w a rd . No m u co u s c e lls a r e p r e s e n t alo n g the flo o r and the l a t e r a l w a lls of the b u c c a l c a v ity in th e 18 re g io n of the o d o n to p h o re. On the w a lls of th e b u c c a l cav ity , im m e d ia te ly in fro n t of the o d o n to p h o re , a r e s itu a te d la te r a lly tw o s e m i c i r c u l a r h o rn y p la te s , the ja w s ( F ig u r e s 17 and 18), w hich c o n s is t of a s e r i e s of c lo s e ly packed light b ro w n d e n tic u la te d co lu m n s lo n g e r in th e c e n te r th an n e a r the m a r g in (F ig u r e 19). E a c h c o lu m n is s e c r e te d by a sin g le c e ll of the e p ith e liu m . Such a s e c r e tin g c e ll p o s s e s s e s an o v al n u c le u s lying in th e b a s a l h a lf of the c e ll. T h e c o lu m n s, w hich fo rm th e jaw , have an a p p e a ra n c e of c r o s s s tr ia tio n s at fa irly r e g u la r in te r v a ls w hich m a y r e p r e s e n t p e rio d ic ity in s e c r e tio n . T h e jaw s have no m a s tic a to r y function but h e lp the r ad u la to g rip and g r a s p food. B eh in d th e ja w s , fro m th e flo o r of the p o s te r i o r p a r t of the b u c c a l ca v ity , the o d o n to p h o re a r i s e s and p r o je c ts fo rw a rd to w a rd the m o u th . T h e o d o n to p h o re is c ro w n e d by th e te e th of th e ra d u la , w hose im m a tu re p o s te r io r end is e n c lo se d in the r a d u la s a c . T h e m u co u s c e lls in th is re g io n of the b u c c a l e p ith e liu m a r e found only in the d o r s a l p h a ry n g e a l c a n a l, the v e n tr a l s u rfa c e of the d o r s o - l a t e r a l folds o v e rla y in g th e o d o n to p h o re , and in th e v e n tr a l s u rfa c e of the o d o n to p h o re . A long the l a t e r a l w a lls of th e b u c c a l c a v ity o c c u r gland c e lls of seco n d type w hich a r e s c a tte r e d am ong the e p ith e lia l c e lls and the m u c o u s c e lls a n te r io r ly , b u t b e c o m e m o re n u m e ro u s to w a rd the p o s te r io r lim it of the o d o n to p h o re . E a c h gland c e ll h a s a la rg e round n u c le u s and a d is tin c t n u c le o lu s. A round th e n u c le u s the c y to p la sm is 19 d e n s e . In the d o r s a l p o s te r i o r p a r t of the b u c c a l c a v ity the c u tic u la te d e p ith e liu m is re p la c e d by c ilia te d c o lu m n a r c e lls w hich f i r s t a p p e a r on the tip of ea c h d o r s o - l a t e r a l lo n g itu d in al fold at th e p o s te r i o r lim it of th e m a n d ib u la r re g io n , and p o s te r io r ly , n e a r the o p en in g s of the s a liv a r y g la n d s, s p re a d a ro u n d th e fold on each sid e on to the p h a ry n g e a l c a n a l. A m ong th e se r e g u l a r c o lu m n a r c e lls w hich h av e elo n g ated g r a n u la r n u c le i s itu a te d to w a rd th e p ro x im a l e n d s, a r e i n t e r s p e r s e d la r g e m u c o u s c e lls . T he o d o n to p h o re ( F ig u r e s 8, 17, and 19) is a p a c k e t-lik e s t r u c tu r e w hich is s u rro u n d e d , e x c e p t at the p o s te r io r end, by a s e r i e s of s tr o n g m u s c le s , w hich s e rv e to d ra w the w hole a p p a r a tu s fo rw a rd and b a c k w a rd . In life th e se m u s c le s a r e of a re d d is h c o lo r due to the p r e s e n c e of h em o g lo b in . T h e o d o n to p h o re is c o v e re d by a cu b o id a l o r low c o lu m n a r e p ith e liu m w ith o v al n u c le i. O v e r the p o s te r io r and d o r s a l fa c e s of th is p a c k e t s tr e t c h e s the ra d u la w hich is ex p o sed p a r tia lly , the r e m a in d e r lying in th e ra d u la sa c e x ten d in g v e n t r a lly fro m th e p o s te r io r lim it of th e b u c c a l m a s s . The ra d u la ( F ig u r e s 8, 18, and 19) is a b ro a d rib b o n (a p p ro x im a te ly 2.5 m m to 3 m m by 4 m m to 4.5 m m ) su p p o rte d by a s u b r ad u la m e m b ra n e in w hich a s e r i e s of t r a n s v e r s e ro w s of c h itin o u s te e th a r e s itu a te d . T h e y a r e two ty p e s of te e th — c e n tr a l and l a te r a l. T h e c e n te r tooth d iff e r s fro m th e l a t e r a l te e th , w hich a r e a ll alik e ( F ig u r e s 25, 26, 27, and 28). E a c h t r a n s v e r s e ro w of te e th d o e s not ru n s tr a ig h t a c r o s s the ra d u la , bu t 20 h a s a s o m e w h a t V -sh a p e c o u r s e . T h e n u m b e r of te e th in the t r a n s v e r s e row v a r i e s fro m 100 to 122 (th is n u m b e r d o es not apply to th a t in the ra d u la s a c ), a r ra n g e d in a 5 0 -6 1 , 1, 50-61 fo rm u la . T he a v e ra g e n u m b e r of ro w s is about 40. H o w ev er, the n u m b e r of te e th and the ro w s m a y d iffe r c o n s id e r a b ly w ith a g e. T he c e n te r tooth is b ro a d w ith th re e c u s p s — the c e n tr a l cu sp b ein g the la r g e s t. T he l a t e r a l s a r e long, s le n d e r , s h a rp te e th , th e c u s p s of w hich n a r ro w down and bend in w ard to w a rd the c e n tr a l te e th and slig h tly p o s te r io r ly . T he f i r s t few l a t e r a l te e th a r e b r o a d e r th a n the r e s t , and th e ir c u s p s a r e slig h tly in clin ed f ro m the c e n tr a l to o th . T h e len g th s of the l a t e r a l te e th g ra d u a lly in c r e a s e fro m the c e n te r to the m a r g in . T h e b a s e s of th e s e te e th a r e e m b e d d e d in the ra d u la m e m b ra n e . T he ra d u la sa c ( F ig u re 18) c o n s is ts of a thin o u te r m u s c le la y e r and an in n e r e p ith e lie l la y e r w hich s e c r e t e s the te e th of the ra d u la . T h is e p ith e liu m is c o m p o se d of low c o lu m n a r c e lls , e a c h w ith a b a s a l o v al n u c le u s and a n u c le o lu s. F r o m the b a s e of the ra d u la s a c a r i s e s a c o lu m n -lik e s tr u c t u r e , the ra d u la c o llo s ty l ( C a r r i k e r , 1947), w hich o c c u p ie s the e n tir e len g th o f the r a d u la s a c and a tta c h e s its e lf to the p o s te r i o r w a ll of the o d o n to p h o re . T he ra d u la c o llo sty l is c a r t i l a g i n o u s, c o n s is tin g of c e lls w ith long c y to p la sm ic p r o c e s s e s , and m u s c le f ib e rs in a ll d ire c tio n s . It is en v elo p ed by the im m a tu re p o rtio n of the r a d u la w hich is clo th ed e x te r n a lly by th e ra d u la s a c . T he ro u n d b a s e 21 of the ra d u la sa c is lined w ith la r g e d eep ly sta in in g c e lls , the o d o n to b la s ts (H offm an, 1939), w hich fo rm the te e th . T he s p a c e s b e tw een te e th and the c o llo s ty l a r e filled by fo llicle c e lls w ith p ro m in e n t n u c le i ( F ig u re 20). A long the d o r s a l re g io n of the b u c c a l c a v ity ru n s the d o r s a l p h a ry n g e a l c a n a l, w hich is c o n s tr ic te d off fro m th e v e n tr a l re g io n of th e c a v ity by two d o r s o - l a t e r a l fo ld s. T h e p h a ry n g e a l c a n a l is lined by a c o lu m n a r e p ith e liu m of w hich the co m p o n en t c e lls hav e elo n g ated n u c le i and a r e th ick ly c o v e re d by a la y e r of s h o rt c ilia . A m ong the c ilia te d c e lls , lie la rg e m u c o u s c e lls w ith b a s a l, i r r e g u l a r l y sh ap ed n u c le i. P o s t e r i o r l y the c ilia te d e p ith e liu m as d e s c r ib e d above s p re a d s down e a c h sid e of the b u c c a l c a v ity to the o pening of the s a liv a r y duct. T h e e p ith e liu m of th e b u c c a l cav ity r e s t s on a b a s e m e n t m e m b ra n e u n d e rlin e d by co n n ec tiv e tis s u e w hich is t r a v e r s e d in a ll d ire c tio n s by m u s c le f ib e r s . E so p h a g u s and a n t e r i o r c r o p . T he d o r s a l p h a ry n g e a l c a n a l of th e b u c c a l c a v ity le a d s to the e s o p h a g u s, w hich r u n s b ack th ro u g h the c e p h a lic h e m o c o e le to the g iz z a r d . It is a n a r ro w th in -w a lle d tube w hich b en d s tw ice , and th en e n la r g e s into th e a n te r io r c ro p . T he f i r s t bend b e a r s a d o r s a l e s o p h a g e a l d iv e rtic u lu m on the top about 0.5 to 1 m m high (F ig u r e 12). T h e seco n d o c c u rs a s the e so p h a g u s p a s s e s th ro u g h th e n e rv e rin g . T h e w a lls p o s s e s s a th in m u s c u la r c o at, and 22 in te rn a lly a r e th ro w n into lo n g itu d in a l fo ld s by v a r ia tio n s in th ic k n e s s of th e u n d e rly in g c o n n e c tiv e t i s s u e . T h e c ilia te d e p ith e liu m , r ic h in m u c o u s c e lls , r e s e m b le s th a t of the p h a ry n g e a l c a n a l. S im ila r c e lls a r e found in the a n te r io r c ro p , but th e c ilia of the c o lu m n a r c e lls a r e d iffic u lt to tr a c e in s e c tio n . G iz z a rd and p o s te r io r c r o p . T he tr itu r a tin g g iz z a r d c o n s is ts of th re e ch itin o u s p la te s — one d o r s a l and two v e n tr o - l a t e r a l ; and a m u s c u la r w all. F r o m the e p ith e liu m o v e rly in g the a n t e r i o r p a r t of the g iz z a r d p la te s a r i s e th r e e th in -w a lle d , g r a n d u la r p o u c h e s, the g iz z a rd d iv e r tic u la ( F ig u re 21). T he g iz z a rd d iv e rtic u lu m p o s s e s s e s an o u te r th in m u s c le la y e r and an in n e r g la n d u la r e p ith e liu m . T h e e p ith e liu m c o n s is ts of la rg e gland c e lls fille d w ith c o lo r le s s s p h e r u le s , s e p a ra te d by s m a ll w e d g e -sh a p e d c e lls . T he n u c le u s of the gland c e ll is b a s a l in p o sitio n , c i r c u l a r in outline w ith a p ro m in e n t n u c le o lu s. T h e c y to p la s m is d e n se aro u n d the n u c le u s a t th e b a se of the c e ll. T he o v al g r a n u la r n u c le u s of the w e d g e -sh a p e d c e ll is s itu a te d in th e b ro a d d is ta l end of the c e ll (F ig u r e 29). T h e th re e g iz z a r d p la te s a r e em b ed d ed in th e p o c k e ts in the g iz z a rd w all. E a c h g iz z a rd plate is d eep ly concave on its o u te r s u r face and convex on its in n e r s u rf a c e ( F ig u r e s 22, 23, and 24), T he d a r k b ro w n convex s u rf a c e o r m a s tic a tin g s u rfa c e is d iffe re n tia te d into a n u m b e r of rid g e s . T h e rid g e s b e a r n u m e ro u s m ic ro s c o p ic 23 s e m i - t r a n s p a r e n t h o rn y te e th ; the l a r g e s t m e a s u re d about 34 m ic r o n s and had a long t r ia n g u la r fo rm . On e a c h p ro m in e n c e b e tw e e n the p la te s is a sin g le c o n ic a l sh ap ed tooth w hich sh o w s a lo n g itu d in al sp littin g fro m the c e n tr a l p a r t. T h e e p ith e liu m w hich lin e s the lu m en of the g iz z a rd p a s s e s ro u n d e a c h p la te , fo rm in g a p o c k e t in w hich the p late lie s , and p r o je c ts into the lu m en b etw een the p la te s fo rm in g the p ro m in e n c e on w hich the c o n ic a l to o th lie s . T h e cu b o id al e p ith e liu m u n d e rly in g the p la te s h a s b a s a l ro u n d o r o v a l n u c le i w ith p ro m in e n t n u c le o li. T h e c y to p la sm a t the d is ta l end of th e e p ith e lia l c e ll is f ib r i l l a r . T h e e p ith e liu m b etw een the p la te s is c o v e re d by c u tic le and s c a tte r e d m u c o u s and gland c e lls . T h e c e lls s e c r e tin g the te e th a r e c o lu m n a r and have b a s a l e lo n g a te d n u c le i. T he b a s e m e n t m e m b ra n e u n d e rly in g th e ep ith e liu m r e s t s upon a la y e r of co n n ectiv e t i s s u e , w hich is m u c h th ic k e r b e n e a th th e p la te s . A few c i r c u l a r and t r a n s v e r s e m u s c le s a r e d ev elo p ed in the co n n e c tiv e tis s u e b e n e ath th e g iz z a r d te e th . T h e g iz z a rd is s u rro u n d e d by a w e ll-d e v e lo p e d c i r c u l a r m u s c le la y e r w hich in c r e a s e s in th ic k n e s s to w a rd the p o s te r io r end (F ig u r e 8). T he p o s te r io r c ro p is a s tr a ig h t tube w hich le a d s fro m the g iz z a rd and p a s s e s f r e e ly th ro u g h a ho le in the d ia p h ra g m into the p o s te r io r body ca v ity . The h is to lo g ic a l d e ta il of the e p ith e liu m c lo s e ly r e s e m b l e s th a t of th e a n t e r i o r c ro p . S to m a c h (F ig u re 12). T he s to m a c h is a so m ew h a t U -sh a p e d , 24 th in -w a lle d s a c , le a d in g p o s te r io r ly fro m the p o s te r i o r c ro p , and lying w ith in the liv e r, w ith its g r e a t e r c u r v a tu re p la c e d d o r s a lly and l e s s e r c u r v a tu re v e n tr a lly . F r o m h e r e on th e d ig e stiv e t r a c t b e c o m e s e m b edded in the d ig e stiv e g lan d . At the a n te r io r end of the s to m a c h ju s t p o s te r i o r to the p o s te r i o r s to m a c h ju n c tio n open th e r ig h t and left h e p a tic d u c ts, fro m w hich a s e r i e s of lo n g itu d in al c ilia te d fo ld s and g ro o v e s p a s s dow n the v e n tr a l s u rf a c e of the s to m a c h ( F ig u r e 13). A m ong th e s e folds the m o s t c o n sp ic u o u s m a jo r fold is s tro n g ly c ilia te d and e x te n d s into the in te s tin e fo r s o m e d is ta n c e . T h e in n e r lining m u c o s a c o n s is ts of c o lu m n a r c ilia te d c e lls , w ith c e n tr a lly lo c a te d n u c le i and h ig h ly v a c u o la te d c y to p la sm , and th re e ty p e s of gland c e lls : m u c o u s, c lu b -s h a p e d gland c e lls (F ig u r e 31, SGC), and p u rp le sta in in g gland c e lls ( F ig u r e 31, S G C '). T he m u c o u s c e ll is s i m i l a r to th o se of the a n t e r io r and p o s te r io r c r o p s . T he c lu b -sh a p e d gland c e ll is filled d is ta lly w ith s m a ll s p h e ru le s and h a s a round b a s a l n u c le u s . T he th ird type of c e ll, w hich s ta in s p u rp le , a r i s e s fro m th e b a s e m e n t m e m b ra n e to a h eig h t n e a r ly eq u al to h a lf th at of the e p ith e liu m ; its s o m e w hat ro u n d o r s lig h tly elo n g a te d n u c le u s is c e n tr a lly p la c e d . B e n e a th th is g la n d u la r e p ith e liu m lie s a th in s u b m u c o s a , in w hich a r e d e v elo p ed c i r c u l a r and so m e lo n g itu d in al m u s c le s . In te stin e and R e c tu m ( F ig u re 12). T he in te s tin e le a d s fro m the s to m a c h on the p o s te r io r v e n tr a l s u rf a c e of the v i s c e r a l m a s s and 25 c u rv e s to the r ig h t sid e of the m a s s to fo rm a U -s h a p e d bend. It then p a s s e s u p w a rd to the left along the d o r s a l s u rfa c e to the a n te r io r p o r tion of the v i s c e r a l m a s s w here it b en d s v e n tra d ag a in to fo rm a sin g le v e n tr a l loop. P a s s i n g tr a n s v e r s e l y b e tw een the s to m a c h and th e v i s c e r a l m a s s it ru n s d o r s a lly along the rig h t d o r s a l sid e of the v i s c e r a l m a s s to the a n u s . On th e b a s is of h is to lo g ic a l d iffe re n c e s , the in te stin e m ay be d iv id ed into th re e s e c t io n s — th e a n te r io r in te s tin e w hich fro m the opening of the s to m a c h c u rv e s to the rig h t sid e and f o rm s a U -s h a p e d band; the m id -in te s tin e w h ich c u r v e s o v e r the v i s c e r a and f o rm s th e v e n tr a l loop; and the s h o r t r e c tu m . T he in te stin e is lined th ro u g h o u t by a c o lu m n a r c ilia te d e p i th e liu m w ith m u c o u s and gland c e lls ; the c ilia te d c e lls r e s e m b le th o se of the s to m a c h . T h e c o lu m n a r e p ith e liu m of the a n t e r i o r in te stin e c o n s i s t s of tw o ty p e s of gland c e lls b e s id e s the c ilia te d and m u c o u s c e lls . One of th e se is the e llip tic a l c e ll, w hich s ta in e d r e d , and h a s a la rg e ov al n u c le u s lo c a te d in th e b a s a l h a lf of the c y to p la s m w hich is filled w ith d a rk ly s ta in e d g r a n u le s . T h e seco n d type is p u rp le w ith slig h tly e lo n g ated o r ro u n d ed n u c le u s lying to w a rd th e c e n te r of the c y to p la sm . E a c h type of g lan d c e ll h a s a s le n d e r du ct le a d in g to the lu m e n of the in te s tin e . T he m id - in te s tin e is c h a r a c te r is e d by the p r e s e n c e of n u m e ro u s gland c e lls s c a tte r e d a m o n g the c o lu m n a r c ilia te d c e lls and m u co u s c e lls . T h e m o s t n u m e ro u s of the gland c e lls a r e th e n a r ro w 26 c lu b -s h a p e d c e lls having a h eig h t s i m i l a r to th a t of the c ilia te d c e lls ; th e y a r e fille d w ith s m a ll s p h e ru le s s ta in in g r e d . T he n u c leu s w hich is lo c a ted b a s a lly is n e a r ly s p h e r ic a l and fille d w ith d a rk ly sta in e d g ra n u le s ( F ig u r e 32, IGC). N e a r the r e c tu m th e se c e lls d e c r e a s e in n u m b e r. O c c a s io n a lly a p p e a rin g in the e p ith e liu m is the sec o n d type of gland c e ll w hich a r i s e s fro m th e b a s e m e n t m e m b ra n e to a h eig h t n e a r ly e q u a l to h a lf th at of the e p ith e liu m ; its b a s a l s p h e r ic a l n u cle u s is l a r g e r th an th a t of any o th e r c e ll. T h e c y to p la sm is d e n se and g r a n u la r . In s o m e s e c tio n s a d u ct can be s e e n lead in g fro m the gland c e ll to the in te s tin a l lu m en ( F ig u re 32, IG C '). T he th ird type of c e ll v a r ie s in s iz e and s h a p e . It h a s an elo n g a te d o r so m e w h a t h o r s e s h o e sh ap ed n u c le u s lying to w a rd the b a s e of the c e ll, w hich alw ay s a p p e a r s v a c u o la te d ( F ig u r e 32, IG C "). T he m u c o u s and the c ilia te d c e lls lying c o m p r e s s e d b e tw e e n th e m a r e s i m i l a r to th o se of the a n t e r i o r i n t e s tin e . T h e e p ith e liu m lie s on th e b a s e m e n t m e m b ra n e and a la y e r of c o n n e c tiv e tis s u e w hich b in d s th e in te s tin e to the liv e r. T h ro u g h the c o n n e c tiv e tis s u e p a s s c i r c u l a r m u s c le f ib e rs and a few lo n g itu d in al f ib e r s . T he r e c tu m , the t e r m in a l p o rtio n of the in te s tin e , is a p p r o x i m a te ly 1.5 m m in length. T h e an u s is situ a te d in the fu rro w b e tw e e n the ro o f and flo o r of the p a llia i c a v ity . T he r e c tu m is lined by c ilia te d c o lu m n a r e p ith e liu m ; the i n t e r c e l lu l a r f ib r illa e a r e s tro n g ly 27 d ev elo p ed . The length of the c ilia te d c e lls d e c r e a s e s to w a rd the lo w e r end of th e r e c tu m ; h e r e th e m u c o u s c e lls b e c o m e m o r e n u m e ro u s . T he seco n d type of gland c e ll found in the m id -in te s tin e is a ls o found h e r e , and h a s a h eig h t s i m i l a r to th a t of the c ilia te d c e lls . T he w a lls of the r e c tu m a r e th ro w n into a n u m b e r of lo n g i tu d in a l folds by the v a r ia tio n s in th ic k n e s s of the u n d e rly in g co n n ectiv e tis s u e . A la y e r of c i r c u l a r and som e lo n g itu d in al m u s c le f ib e rs is d e v elo p ed in the c o n n ec tiv e tis s u e ; the c i r c u l a r f ib e r s fo rm a s p h in c te r a ro u n d the a n u s. F r e e a m o e b o c y te s a r e found in the s to m a c h and in te stin e lying b e n e a th the w a lls o r in v a c u o le s in the e p ith e liu m ( F ig u r e s 31 and 32). T h e s e a r e s m a ll c e lls w ith fine p ro to p la s m ic p se u d o p o d ia l p r o c e s s e s . T h e d a rk ly sta in in g n u c le i of v a r io u s sh a p e s co n ta in la r g e c h ro m a tin g ra n u le s th a t sta n d out a g a in s t the lig h tly sta in in g c y to p la s m . T h e se a m o e b o c y te s a r e a ls o found in the co n n ectiv e tis s u e b e n e a th the e p ith e liu m of the d ig e stiv e g land and the blood v e s s e l s . D ig e s tiv e G lan d s S a liv a ry g la n d . S p re a d in g a ro u n d the a n t e r i o r p a r t of the g iz z a r d a r e two elo n g a te d s a liv a r y g lan d s w hich a r e a tta c h e d by c o n n e c tiv e tis s u e to the g iz z a r d and p a s s fo rw a rd along e a c h sid e of the e so p h a g u s ( F ig u r e 12). J u s t b eh in d th e n e rv e rin g the g la n d u la r tis s u e of the gland s to p s . T h e d u c t p o rtio n s of the o rg a n s ru n th ro u g h the 28 n e rv e rin g and ex ten d into the m u s c le on th e d o r s a l sid e of the b u c c a l m a s s to o p en la te r a lly on e ith e r s id e of the o d o n to p h o re. E a c h s a liv a r y gland c o n s is ts of a n u m b e r of s m a ll tu b u le s lin ed w ith e p ith e liu m c o m po sed of c ilia te d and gland c e lls . M ost of the gland c e lls a r e la rg e and d eep ly sta in in g cu b o id al c e lls w ith la rg e o v al o r i r r e g u l a r n u c le i lo c a te d in th e c e n te r (F ig u r e 33, SAGC). T h e se c o n d type of gland c e ll is a lig h tly s ta in in g , s m a l l e r , c o lu m n a r c e ll filled w ith v a c u o la te d c y to p la sm ( F ig u r e 33, SAGC'). In th e tu b u le s and the d is ta l re g io n of the d u ct, c ilia te d c e lls a r e w edged b e tw e e n th e s e gland c e lls . T h e o v al n u c le i a r e fre q u e n tly s itu a te d in the d is ta l e n d s of the c e lls . A s the d u ct p a s s e s to w a rd th e n e rv e rin g , the c ilia te d c e lls b e c o m e cu b o id al in o u tlin e and in c r e a s e in n u m b e r, and g ra d u a lly r e p la c e th e gland c e lls . In th e p r o x im a l p a r t of the d u ct, a t th e point w h e re it e n t e r s the m u s c u la r w all of the b u c c a l m a s s , a n o th e r type of la rg e gland c e ll co n tain g d a r k ly sta in in g s e c r e tio n d r o p le ts (F ig u re 34, SDGC) is found am o n g the c ilia te d c e lls . Its o v a l n u c le u s is p la ce d n e a r the c e ll m e m b r a n e . T h is type of g la n d u la r e p ith e liu m lin e s the r e s t of th e duct ( F ig u r e 34). T h e tu b u le s a r e bound to g e th e r by u n d e rly in g c o n n ectiv e tis s u e , w h ich c o n tin u e s w ith th e c o n n ectiv e tis s u e u n d e rly in g the e p ith e liu m of the d u ct. Som e c i r c u l a r m u s c le s a r e d ev e lo p e d in the c o n n ectiv e tis s u e a ro u n d the p r o x im a l p a rt of th e d u ct. 29 L i v e r . T he liv e r , o r d ig e s tiv e gland, is a v o lu m in o u s o liv e - g re e n gland w hich to g e th e r w ith th e gonad and its d u ct m ak e up the v i s c e r a l m a s s w hich is im m e d ia te ly p o s te r io r to the h e a r t. It o c c u p ie s th e g r e a t e s t p a r t of the v i s c e r a l h e m o c o e le and fo rm s a su p p o rt fo r the s to m a c h and c o ils o f the in te s tin e . T he gland c o n s is ts of a n u m b e r of tu b u le s bound to g e th e r by c o n n e c tiv e tis s u e in w hich m an y a m o e b o c y te s w ith p ro m in e n t n u c le i a r e found. T h e in n e r lin in g of e a c h tu b u le c o n s is ts of two ty p es of c e lls : (1) c e lls r ic h in d ig e s tiv e s e c r e tio n s, and (2) c e lls low in c y to p la s m , but u s u a lly h ig h ly v a c u o la te d and full of in c lu s io n s , and e x c r e to r y in fu n ctio n (F ig u r e 30). T h e f o r m e r , the d ig e stiv e c e lls , a r e ta ll, n a r ro w a t the b a s e and b ro a d a t th e d is ta l end; the ov al n u c le u s is s itu a te d to w a rd th e b a s e of the c y to p la sm ; w h ich , in s e c tio n , is filled w ith light p u rp le o r re d d is h s p h e r u le s , and fre q u e n tly d ro p s of o il. T h e l a t t e r , th e e x c re tin g c e lls , a r e tr ia n g u la r in s e c tio n , the w idth a t the b a se of th e c e ll m a y e x c e e d th e h eig h t. T h e s e e x c r e tin g c e lls u s u a lly o c c u r in c l u s te r s in the c r y p ts of the tu b u le s. T h e round n u c le u s is l a r g e r th an th a t of the d ig e stiv e c e ll, and e a c h h a s a p ro m in e n t n u c le o lu s. T h e c y to p la sm is v a c u o la te d , co n tain in g la r g e in c lu sio n s w hich fre q u e n tly r e ta in th e ir g r e e n is h b ro w n c o lo r a f te r th e c e ll h a s b een s ta in e d . In so m e c e lls , th e s e in c lu s io n s a r e so lid , i r r e g u l a r s p h e r ic a l m a s s e s ; in o th e r s th e r e is only an i r r e g u l a r c e n tr a l m a s s in a v a c u o le -lik e p o rtio n of the c e ll. T he tu b u le s jo in to g e th e r to fo rm c ilia te d c a n a ls , the h e p a tic d u c ts . 30 w hich a r e of w ide d i a m e te r and d is c h a rg e by tw o o p en in g s into the a n t e r i o r lim it of the s to m a c h ju s t behind the p o s tc ro p - s to m a c h ju n ctio n ( F ig u r e s 12 and 13). T h e c ilia te d c o lu m n a r e p ith e liu m of the c a n a l is th ro w n into a s e r i e s of lo n g itu d in al fo ld s w hich p a s s dow n th e v e n tr a l s u rf a c e of the s to m a c h . T h e c ilia te d lining is s i m i l a r to th a t of the s to m a c h , and s tr i p s of th is e p ith e liu m p e n e tra te the d e p th s of the liv e r . T h e c o lu m n a r n o n -c ilia te d c e lls and the few m u c o u s c e lls fo rm a tra n s itio n zone b e tw e e n the c ilia te d c e lls of the d u c t and the c e lls of the d ig e stiv e gland. C ir c u la to r y S y ste m T h e v a s c u la r s y s te m is m a d e up of a tw o -c h a m b e re d h e a r t, a r t e r i e s , v e in s , and la c u n a e ( F ig u r e s 5 and 6). T h e s p a c io u s p e r i c a r d ia l ca v ity , th e tr u e c o e lo m , s itu a te d im m e d ia te ly a n t e r io r to the v i s c e r a l m a s s c lo s e u n d e r th e a n te r io r edge of th e s h e ll, is lined by a th in m e m b ra n e w ith in te rla c in g m u s c le f ib e r s . T he h e a r t, c o n s is tin g of a m u s c u la r v e n tr ic le and a th in -w a lle d a u r ic le , o c c u p ie s the p o s te r i o r p o rtio n of the c a v ity . T he a u r ic le , w hich is on th e rig h t, h a s th e a p p e a ra n c e o f la c e ow ing to the p r e s e n c e of in te rla c in g m u s c le and fib ro u s tis s u e in its w a lls . T he v e n tr ic le on th e le ft, is s e p a ra te d fro m the l a r g e r a u r ic le by a p a i r of s e m ilu n a r v a lv e s ( F ig u r e 7). T h e r e is no e n d o th e lia l tis s u e lining the ca v ity of the h e a r t so th a t the m u s c le f ib e r s of the w a lls a r e d ire c tly in c o n ta c t w ith th e blood 31 ( F ig u r e 36). T h e a u r ic le r e c e iv e s blood fro m th e k idney and the c te n id iu m by the r e n a l v ein and the b r a n c h ia l v ein re s p e c tiv e ly . T he v e n tr ic le g iv e s off a co m m o n a o r ta w hich soon s e n d s out the h e p a tic a r t e r y . S h o rtly a f te r le av in g th e co m m o n a o r ta the h e p a tic a r t e r y tu r n s p o s te r io r ly to e n te r th e liv e r w h e re it f u r t h e r b r a n c h e s into s m a ll a r t e r i e s . T h e co m m o n a o r ta th en d iv id e s into (1) the p o s te r i o r a o r ta ru n n in g b a c k w a rd to su p p ly the o rg a n s in th e v i s c e r a l m a s s , i . e . , the gonad, liv e r , and th e lo w e r p o rtio n of th e a lim e n ta ry c a n a l; (2) a s m a l l e r g a s tr o - e s o p h a g e a l a r t e r y , a r is in g at the point w h e re th e c o m m on a o r ta d iv id e s into a n t e r i o r and p o s te r io r a o r ta , to su p p ly the g iz z a rd and the e so p h a g u s; and (3) an a n t e r i o r a o r ta , w hich ru n s a c r o s s the flo o r and to the rig h t of th e p e r i c a r d i a l c a v ity and se n d s out a b ra n c h , the g e n ita l a r t e r y , to th e g e n ita l o rg a n s ( a c c e s s o r y g e n ita l g la n d s). T h e a n t e r i o r a o r ta th en p a s s e s b e n e a th the s p e r m a th e c a and g iv e s off b r a n c h e s to the re g io n of the lo w e r p a r t of the g e n ita l d u ct. T h e r e m a in d e r of th e a o r ta then tu rn s a n te r io r ly along the rig h t sid e of the body w a ll to the head re g io n (F ig u r e 6). T he b ra n c h e d a r t e r i e s em p ty into n u m e ro u s i r r e g u l a r s p a c e s , la c u n a e , in the tis s u e s . A s in the c a s e of th e w a lls of the h e a r t, the la c u n a e a r e not lined by e p i th e liu m . R e tu rn in g to the h e a r t, the blood fro m th e lacu n ae in the v a rio u s p a r ts of the body is c o lle c te d in th e body c a v ity , h e m o c o e le , fro m w hich the blood d r a in s into a s e r i e s of s in u s e s . T h e se s in u s e s e v e n tu a lly open into a la rg e s in u s s itu a te d b e n e a th the flo o r of the 32 p a llia i c a v ity p o s te r io r to th e kidney and the c te n id iu m . F r o m th is s in u s th e blood is d is c h a rg e d e ith e r to th e kidney o r to th e c te n id iu m . T he blood in the c te n id iu m is o x y g en ated and c o lle c te d in tw o e ffe re n t v e s s e ls ; fro m w hence it e n te r s the b r a n c h ia l v e s s e l w hich le a d s to the rig h t sid e o f th e a u r ic le . The blood fro m the k id n ey , a f te r being p u r i fied fro m n itro g e n o u s w a s te , e n te r s the s h o r t r e n a l v e in s itu a te d on the m i d - d o r s a l s u rf a c e of th e k id n ey . T h e r e n a l v e in opens into the r ig h t sid e of th e a u r ic le d o r s a l to th e opening of th e b r a n c h ia l v ein . A ll the v e s s e ls a r e lined by t i s s u e s s i m i l a r to th o se of the p e r ic a r d iu m . R e s p ir a to r y S y ste m T he c te n id iu m , a p in n a te ly com pound le a f-lik e s tr u c t u r e , e x te n d s a c r o s s the ro o f of th e m a n tle c h a m b e r ( i . e . , on th e u n d e rs id e of the m a n tle ). O ne h a lf of the c te n id iu m is a tta c h e d to th e v e n t r o - l a t e r a l p o rtio n of th e k id n ey by the p o s te r i o r e ffe re n t v e s s e l. T h e o th e r u n a tta c h e d h a lf c u r v e s p o s te r io r ly . T h e a n te r io r and p o s te r io r e ffe re n t v e s s e ls ru n alo n g th e a n t e r o - v e n t r a l sid e of the g ill; on e a c h sid e of w hich a r e ra n g e d th e p in n u le s, the g r e a te s t o n es b ein g lo c a te d c e n tr a lly . T h e a ffe re n t v e s s e l e x te n d s along the p o ste r o - d o r s a l co n cav e s id e of th e c te n id iu m ( F ig u r e 5). B oth b r a n c h ia l v e s s e l s a r e co m p o se d of an o u te r c u b o id al e p ith e liu m and an in n e r la y e r o f lo o se tis s u e c o n s is tin g of co n n ectiv e and m u s c le f ib e rs . T h e a ffe re n t v e s s e l 33 c o m m u n ic a te s w ith th e g ill pin n u le o r la m e lla by a la rg e opening th ro u g h w h ich the blood p a s s e s to the c e n tr a l sp a c e b etw een the two la m in a e w hich to g e th e r c o n s titu te th e la m e lla , w hich in tu rn o p en s into th e e ffe re n t v e s s e ls ( F ig u r e 9), T he p o s te r io r and the a n t e r io r e ffe re n t v e s s e l s jo in to fo rm the e ffe re n t b ra n c h ia l v e s s e l a t the ju n c tio n of the c te n id iu m and the k id n ey . E a c h pinnule c o n s is ts of an e x te r n a l e p ith e liu m of i r r e g u l a r l y a r r a n g e d c e lls and a c e n tr a l sp a c e lin ed by a th in la y e r of lo o se c o n n e ctiv e tis s u e . In so m e p a r t s of the e p ith e liu m , e s p e c ia lly n e a r the ju n c tio n of the p in n u les and the e ffe re n t and a ffe re n t v e s s e ls , la r g e gland c e lls a r e in te r s p e r s e d . T he sp a c e b e tw e e n th e la m in a e of th e g ill pinnule is b ro k e n up into n u m e ro u s s m a ll c h a n n e ls by the p r e s e n c e of g r e a t n u m b e rs of i n te r la m in a r c o n n e c tio n s ex ten d in g a c r o s s the s p a c e and jo in in g the tw o la m in a e w hich c o m p o se the g ill p in n u le. E x c r e to r y S y ste m The so m ew h a t tr ia n g u la r n e p h rid iu m o r kidney, is s itu a te d on the rig h t s id e of the liv e r lying c lo s e u n d e r the m a n tle . It is s e p a r a te d fro m th e v i s c e r a l m a s s e x c e p t at th e left m a r g in w h e re it is a tta c h e d to the m a s s by c o n n ectiv e tis s u e . T he b a s e of the kidney e x te n d s f o r w a rd to th e p e r ic a r d iu m , p o s te r io r ly th e apex of the tria n g le r e a c h e s the le v e l of th e r e c tu m and the p o s te r i o r a tta c h m e n t of the g ill. It c o m m u n ic a te s w ith th e p a llia i c a v ity p o s te r io r ly by a m in u te opening 34 (15 m ic ro n s ) , the r e n a l p o re (F ig u r e 5), v e n tr a lly s itu a te d on a s m a ll p a p illa n e a r the ro o t of th e c te n id iu m . T h e k id n ey e m p tie s its p ro d u c ts d ir e c tly th ro u g h the r e n a l p o re . A t the a n t e r i o r end of the k id n ey the r e n a l v e in , lead in g fro m the c a v ity of r e n a l s a c , ex ten d s into th e p e r i c a r d ia l ca v ity and e n te r s the a u r ic le a t a point p a r a lle l w ith the b r a n c h i a l v ein . T h e k id n ey is c o m p o se d of p a r a lle l la m e lla e e n c a s e d in a th in c o n n ectiv e tis s u e c a p s u le . E a c h la m e lla is c o m p o se d of tw o la y e r s of lo o se ly a r r a n g e d g la n d u la r c e lls lying a g a in s t e a c h o th e r, and betw een th e s e tw o la y e r s is a blood s in u s . T h e g land c e lls v a ry in s iz e and sh a p e , and u s u a lly have la rg e c e n tr a l v a c u o la te d a r e a s , so m e of w hich co n ta in d a rk ly s ta in in g g lo b u les of e x c r e to r y m a t t e r . T h e se m a s s e s , a f te r p a s s in g to the d is ta l en d s of the c e lls , a r e th en cu t off and c a r r i e d th ro u g h the r e n a l p o re to the e x t e r i o r ( F ig u re 37). N e rv o u s S y stem and S en se O rg a n s N e rv o u s S y ste m T h e c e n tr a l n e rv o u s s y s te m c o n s is ts o f th r e e p a ir s of m a jo r g a n g lia. T h e c e r e b r a l, lying on e a c h sid e of th e e so p h a g u s; the p ed al, lying v e n tr a l to the c e r e b r a l; and tne p le u r a l b etw e en the c e r e b r a l and the p ed al g a n g lia c o n s titu te the m a jo r g an g lia. T he c e r e b r a l, p le u ra l, and p e d a l g a n g lia a r e linked to e a c h o th e r by c e r e b r o - p l e u r a l , p le u r a l- p ed al, and c e r e b r o - p e d a l c o n n e c tiv e s , lying c lo se to g e th e r but d is tin c t fro m e a c h o th e r on e a c h sid e of the e so p h a g u s ( F ig u re 39). 35 T he long p e d a l (and p a ra p e d a l) and c e r e b r a l (and s u b c e r e b r a l) c o m m i s s u r e s w ith the tw o g an g lio n ic g ro u p s fo rm a n e rv e r in g c lo se behind the e s o p h a g e a l d iv e rtic u lu m (F ig u r e 38). C e r e b r a l g an g lia and n e r v e s . T h e two c e r e b r a l g a n g lia a r e so m e w h a t tr ia n g u la r in sh a p e and a r e jo in e d by the c e r e b r a l c o n n e c tiv e . A s m a ll a d d itio n a l s u b c e r e b r a l co n n ec tiv e a r i s e s fro m the v e n tr a l s u rf a c e of e a ch gan g lio n and ru n s u n d e r the e s o p h a g u s w ith th e p e d a l c o n n e c tiv e . E a c h c e r e b r a l g an g lio n is lin k ed by c o n n e c tiv e s to both the p le u r a l and p ed al g a n g lia on its own s id e . T he c e r e b r a l g a n g lia a r e th e m a in s e n s o r y c e n te r s fro m e a c h of w hich s ix n e r v e s o rig in a te : 1. T h e long s to m a to g a s tr ic c o n n ectiv e a r i s e s fro m the an te r o - v e n t r a l s u rf a c e of e a c h c e r e b r a l gan g lio n . T h e y ru n a c r o s s to the w a ll of the b u c c a l m a s s , p e r f o r a te th e m u s c u la r w a ll of the l a t t e r , e m e r g in g into view a g a in c lo se u n d e r the s a liv a r y g lan d s; and th en jo in the b u c c a l g a n g lia lying o n the p o s te r io r s u rf a c e of th e b u c c a l m a s s below the e s o p h a g u s. T he tw o b u c c a l g a n g lia a r e u n ited by a s h o rt co n n e c tiv e w hich g iv e s r i s e to a m e d ia n ra d u la n e rv e , ru n n in g dow nw ard into th e m u s c le of the b u c c a l m a s s and e n te r s the r a d u la s a c . T h e s m a ll s a liv a r y n e r v e a r i s e s b e fo re the s to m a to g a s tr ic c o n n e c tiv e jo in s th e g an g lio n (F ig u r e 15). 36 T h e la r g e s to m a to g a s tric n e r v e , w hich a r i s e s fro m the a n t e r i o r p o rtio n of e a c h b u c c a l g anglion n e a r the ju n c tion of the ganglion and the s to m a to g a s tr ic c o n n e c tiv e , ru n s p o s te r io r ly along the e so p h a g u s to su p p ly th e g iz z a rd . A s m a ll b r a n c h is g iv en off to th e point of the o rig in of the e so p h a g u s. 2. A v e r y s le n d e r optic n e rv e a r i s e s d o r s a lly c lo se to the o rig in of e a c h la rg e te n ta c u la r n e r v e . It ru n s u p w ard to the ro o f of the c e p h a lic sh ie ld and in n e r v a te s the e y e. 3. A la r g e , s h o r t te n ta c u la r n e rv e a r i s e s e x te r n a l to the optic n e rv e f ro m th e d o r s a l s u rf a c e of e a c h of th e c e r e b r a l g an g lio n . T h is im m e d ia te ly r u n s u p w ard to th e ro o f of the c e p h a lic sh ie ld and b ra n c h e s to su p p ly the te n ta c le and t i s s u e s of the c e p h a lic s h ie ld . 4. E a c h n e rv e of th e rh in o p h o re is a la r g e n e rv e w h o se o rig in is c lo s e to th a t of the te n ta c u la r n e r v e . T h is n e rv e ru n s la te r a lly and d iv id e s into m an y s h o r t b r a n c h e s , a ll of w hich su p p ly th e rh in o p h o re . 5. T h e la b ia l n e r v e s a r e th e la r g e s t n e r v e s w hich a r i s e fro m the a n t e r i o r s u rf a c e of th e c e r e b r a l g a n g lia and ru n fo rw a rd alo n g the b u c c a l m a s s . E a c h s p lits im m e d ia te ly into two m a jo r b r a n c h e s — a s u p e rf ic ia l and a d eep b ra n c h . T he f o r m e r g iv e s off a b ra n c h to the te n ta c le and th e n b ra n c h e s 37 to su p p ly the palp re g io n . T he la tte r d iv id e s into two b r a n c h e s — the l a r g e r one, ru n n in g along the foot to su p p ly the o r a l s p h in c te r; the s m a l l e r one, a f te r giving off a b ra n c h to the a n t e r i o r re g io n of the rh in o p h o re , in n e r v a te s the palp. A s m a ll n e rv e a r i s e s fro m the ante r o - v e n t r a l p o rtio n of e a c h c e r e b r a l g an g lio n and ru n s fo rw a rd to the v e n tr a l sid e of the m o u th re g io n . 6. T h e s le n d e r a u d ito ry n e rv e a r i s e s fro m th e an te r o - v e n t r a l s id e of ea c h c e r e b r a l g an g lio n b etw een c e r e b r o - p e d a l and c e r e b r o - p l e u r a l c o n n e c tiv e s and ex ten d s p o s te r io r ly to the o to c y st on the an te r o - l a t e r a l s u rfa c e of the p e d al gan g lio n . P e d a l g a n g lia and n e r v e s . T h e p a ire d p ed al g a n g lia a r e a s big a s the c e r e b r a l g a n g lia and lie im m e d ia te ly v e n tr a l to the c e r e b r a l g a n g lia . E a c h p e d a l g an g lio n is c o n n e c te d to th e c e r e b r a l and p le u ra l g a n g lia by m e a n s of c e r e b r o - p e d a l and p le u ro -p e d a l c o n n e c tiv e s r e s p e c tiv e ly . T he two p e d a l g a n g lia a r e c o n n ected by two c o m m i s s u r e s , the p e d a l and p a r a p e d a l c o m m i s s u r e s . T he c o n sp ic u o u s p e d a l c o m m is s u r e lie s v e n tr a l to the e s o p h a g u s. T h e long s le n d e r p a ra p e d a l c o n n e c tiv e , a tta c h e d to the m u s c u la r b an d s of the foot, jo in s th e ro o ts of th e in n e r m o s t p o s te r io r p e d a l n e rv e on e a c h sid e . T he o to c y st is s itu a te d on the a n t e r o - l a t e r a l p o rtio n of the g an g lia. Six n e r v e s a r i s e 38 d ir e c tly fro m e a c h p e d a l ganglion: 1. T h e a n te r io r p ed al n e rv e a r i s e s fro m the a n te r io r p o rtio n of e a c h p e d al g an g lio n , ru n n in g fo rw a rd and b ra n c h in g to in n e rv a te th e a n t e r i o r p o rtio n of the foot. 2. F r o m th e l a t e r a l sid e of e a c h p e d a l ganglion a r i s e s a p a r a p e d al n e r v e , w hich p a s s e s la te r a lly and b r a n c h e s to su p p ly the p a ra p o d iu m . 3. F r o m the p o s te r o - d o r s a l sid e of the p e d a l g an g lio n a r i s e th r e e p o s te r i o r p e d a l n e r v e s , of w hich the in n e r tw o a r e la rg e and the th ir d , the o u te r m o s t, is v e r y s le n d e r . T h e se n e r v e s p a s s p o s te r io r ly into the m a in p o rtio n of th e foot, 4. A m id d le p ed al n e rv e ( F ig u r e 39) a r i s e s fro m the m id - v e n tr a l sid e of e a c h p e d a l g an g lio n and e n te r s d ir e c tly into the foot in the re g io n of the g an g lio n . P l e u r a l g an g lia and n e r v e s . T he p le u r a l g a n g lia a r e situ a te d b e tw een th e c e r e b r a l and p e d a l g an g lia w ith w hich th ey a r e u n ite d by s h o rt and s to u t c e r e b r o - p l e u r a l and p le u r o -p e d a l c o n n e c tiv e s r e s p e c tiv e ly . T he rig h t p le u r a l g anglion a d jo in s the rig h t p a r ie ta l g an g lio n , fro m w hich a r i s e s the la rg e b r a n c h io - p a r ie ta l co n n e c tiv e ru n n in g alo n g th e r ig h t sid e of the body c a v ity to jo in the b r a n c h ia l g an g lio n a t the le v e l of the g iz z a rd . A s m a ll r ig h t m a n tle n e r v e , w hich a r i s e s la te r a lly f ro m th is c o n n e c tiv e , in n e r v a te s the a n t e r i o r p a r t of the 39 m a n tle . T he b r a n c h ia l g an g lio n , fro m its p o s te r o - d o r s a l s id e , g iv es r i s e to the b ra n c h io - os ph r a d ia l n e rv e w hich d iv id e s into th r e e b ra n c h e s — the p o s te r io r o s p h r a d ia l n e rv e and its g an g lio n lying d ir e c tly b en e ath the o s p h ra d iu m ; the m e d ia n b r a n c h ia l n e rv e su p p ly in g the cten id iu m ; and the a n te r io r b ra n c h w hich en d s in a s m a ll g an g lio n s itu a te d on the rig h t edge of the m a n tle . F r o m the p o s te r i o r end of the b r a n c h ia l g an g lio n e x te n d s the long rig h t v i s c e r a l c o m m is s u r e w hich r u n s b a c k w a rd , l a t e r a l to the d ig e s tiv e t r a c t , th en a c r o s s the le ft v i s c e r a l c o m m is s u r e to jo in the v i s c e r a l g anglion along w ith a g an g lio n ic m a s s know n a s the g e n ita l g an g lio n . T h e v i s c e r a l g an g lio n lie s u n d e r the p o s te r i o r lim it of the g iz z a r d and g iv es off the v i s c e r a l n e rv e to su p p ly the v i s c e r a . The g e n ita l ganglion is lo c a te d to the left of the v i s c e r a l g an g lio n and g iv es r i s e to a g e n ita l n e rv e w hich b r a n c h e s to in n e rv a te the g e n ita l o rg a n s . F r o m th e le ft p le u r a l ganglion ex ten d s th e left v i s c e r a l c o m m i s s u r e w hich ru n s v e n tr a lly to the v i s c e r a l g an g lio n re g io n w h e re it s w e lls to fo rm the s u b in te s tin a l g an g lio n lying im m e d ia te ly a n te r io r to the v i s c e r a l gan g lio n . T h e left m a n tle n e rv e a r i s e s fro m the v i s c e r a l f c o m m is s u r e n e a r the p le u r a l g anglion, it r u n s fo rw a rd fo r a v e ry s h o rt d is ta n c e , th en tu r n s b a c k w a rd to ru n w ith th e v i s c e r a l loop fo r so m e p a r t of th e ir le n g th s. It in n e r v a te s the p o s te r io r p a r t of th e m a n tle . T h e w hole of th e n e rv o u s s y s te m , both c e n tr a l and p e r ip h e r a l, is s h e a th e d in a th in c o n n e c tiv e tis s u e e n v e lo p e , in w hich n u m e ro u s 40 blood s in u s e s a r e s itu a te d . T he g an g lio n ic c e lls w ith la rg e i r r e g u l a r l y sh ap ed n u c le i a r e lo c a te d p e r ip h e r a lly in th e ganglion, th e c e n te r of w hich is o c cu p ie d by a g r e a t m a s s of fib ro u s tis s u e , and i n t e r s p e r s e d w ith s m a ll n e u ro g lia c e lls (F ig u r e 41). Tw o g ian t ganglionic c e lls , r e a c h in g a d ia m e te r of 145 m ic ro n s by 182 m ic r o n s , a r e found in the b r a n c h ia l g an g lio n w hile the g r e a t e s t d i a m e te r of the w hole g an g lio n is 233 by 400 m ic r o n s . T h e n e rv o u s s y s te m is the s tr e p to n e u r o u s ty p e, i . e . , th e long v i s c e r a l c o m m is s u r e s a r e tw iste d into a fig u re eig h t. S e n se O rg a n s T he s e n s e o rg a n s a r e the p a ire d e y e s , p a ire d rh in o p h o re s , p a ir e d o to c y s ts , and a sin g le o s p h ra d iu m . E y e s . E a c h eye is s itu a te d n e a r the in n e r b a s e of th e a u r ic u - la te d te n ta c le on e a c h sid e of the c e p h a lic s h ie ld . T h e y a r e s e e n in life a s b la c k sp o ts s u rro u n d e d by c l e a r c i r c u l a r a r e a s of u n p ig m en te d e p id e r m is . T h e se o rg a n s of s ig h t a r e s p h e r ic a l v e s ic le s lying ju s t b e n e a th the s u rf a c e e p id e r m is of the h e a d . E a c h eye c o n s is ts of the follow ing p a r ts : c o rn e a ; re tin a ; le n s; optic c a p su le ; and the optic n e r v e . T h e optic v e s ic le is a sin g le la y e r s a c . T he c o rn e a is the p o rtio n d ir e c tly b e n e a th the e p id e r m is and is c o m p o se d of a s im p le cu b o id a l e p ith e liu m w ith s p h e r ic a l n u c le i. T h e l a t e r a l and in te rn a l p o rtio n s of th e s a c f o rm the r e tin a w hich c o n s is ts of p ig m en ted 41 su p p o rtin g c e lls w ith s m a ll n u c le i and s e n s o r y c e lls w ith la r g e ro u n d n u c le i. T he r e tin a show s th re e z o n e s. T h e o u te r zone w hich is in c o n ta c t w ith th e c a p s u le , is f re e fro m p ig m e n t and c o n ta in s th e c e ll’s n u c le i. T he m id d le zone is the p ig m e n t zone w h e re the p ig m e n ts of the n o n - s e n s o r y c e lls a r e a g g re g a te d . T h e in n e r zone c o n ta in s th e s o - c a lle d “ S tiftc h e n p in s e l” ( M a rc u s , 1956), th e b r u s h - s h a p e d ro d s , w hich a r e the p h o to -re c e p tiv e p o rtio n s of the s e n s o r y c e lls th a t c o n tinue th ro u g h the p ig m e n t zone. T he len s is a g e la tin o u s n o n - c e llu la r s tr u c tu r e o ccu p y in g a lm o s t the e n tir e c a v ity of th e optic v e s ic le ( F ig u r e 40). T he e n tir e eye is c o v e re d , w ith the e x c e p tio n of the c o r n e a l a r e a , by a th in c o n n e c tiv e tis s u e la y e r, the optic c a p s u le , to w hich the optic v e s ic le is a tta c h e d . Som e m e s o d e r m a l p ig m e n t c e lls a r e found in the tis s u e of the c a p s u le . T h e eye is in n e rv a te d by the s le n d e r optic n e rv e fro m th e c e r e b r a l gan g lio n . O s p h ra d iu m . T h e sin g le o s p h ra d iu m is a s m a ll c i r c u l a r p atch (about 300 m ic r o n s in d ia m e te r ) , lo c a te d im m e d ia te ly a n te r io r to the a n t e r i o r a tta c h m e n t of the c te n id iu m ( F ig u r e 5). It is a c h e m ic a l te s tin g o rg a n w hich ^‘t a s t e s ” the w a te r p a s s in g o v e r th e c te n id iu m . T h is s e n s o r y o rg a n is a th ic k e n e d p a tch of n o n -c ilia te d c o lu m n a r e p ith e liu m w h ich c o n s is ts of c e lls of d iffe re n t h e ig h ts w ith o v al o r slig h tly e lo n g a te d n u c le i. In the u n d e rly in g tis s u e of th is e p ith e liu m is 42 s itu a te d the o s p h ra d ia l g an g lio n (F ig u r e 9) fro m w hich s e n s o r y n e r v e s a r i s e . T he s ta lk of th is g an g lio n o rig in a te s fro m the b r a n c h o - o s p h ra d ia l n e rv e . O to c y sts (o r S ta to c y s ts ). T h e se o rg a n s of o r ie n ta tio n a r e p a ire d , e m b e d d e d in th e c o n n e ctiv e tis s u e s h e a th on th e o u te r d o r s a l face of the p e d a l g an g lia ( F ig u r e 39). T h ey a r e in n e rv a te d by s m a ll a u d ito ry n e r v e s fro m the v e n tr a l sid e of th e c e r e b r a l g a n g lia , b etw een the c e r e b r o - p e d a l and the c e r e b r o - p l e u r a l c o n n e c tiv e s . T h e o to c y st is a c lo se d v e s ic le (102 m ic r o n s by 58 m ic ro n s ), w h o se w a ll c o n s is ts of a fla tte n e d n o n -c ilia te d e p ith e liu m w ith elo n g ated n u c le i, and u n d e r lin ed by a th ick b a s e m e n t m e m b ra n e and a th in la y e r of c o n c e n tric a lly a r r a n g e d s h e a th s of c o n n e c tiv e tis s u e . W ithin the c a v ity of the o to c y st a r e m an y c a lc a r e o u s o to lith s w hich a r e s m a ll o v al b o d ie s v a ry in g g r e a tly in s iz e (F ig u r e 41). R h in o p h o r e s . T he r h in o p h o re s , w hich a r e c o n s id e re d to be o lfa c to ry o rg a n s , a r e yellow p e c tin a te o rg a n s in th e liv in g a n im a l. T h ey a r e s itu a te d on e a c h sid e of th e a n te r io r body w a ll b e tw e e n the c e p h a lic sh ie ld and the p a ra p o d iu m and e x ten d in g a n te r io r ly to continue w ith the p alp s w hich a r i s e as fo ld s fro m the body w all a n t e r i o r to the r h in o p h o re s on e a c h s id e of th e m o u th . T h e se o r g a n s e x ten d to the p o s te r io r lim its of the f r e e p a r t of th e c e p h a lic sh ie ld . T h e e p ith e liu m is c o m p o se d of c o lu m n a r c e lls w ith b a s a l ov al 43 n u c le i. T h e c y to p la s m above the n u c le u s is h ig h ly v a c u o la te d and in the d is ta l end of e a c h c e ll sh o w s a d iffe re n t s ta in in g r e a c tio n th a t g iv es th e a p p e a ra n c e of an a d d itio n a l la y e r o v e r the top of the c o lu m n a r e p i th e liu m . T h e cu b o id al s e n s o r y c e lls , la r g e n u c le i and long c ilia , a r e s itu a te d in m in u te p its s c a tte r e d am o n g the e p ith e lia l c e lls ( F ig u r e 35). E a c h le a fle t of the rh in o p h o re is w ell su p p lied by n e rv e b r a n c h e s fro m the c e r e b r a l gan g lio n . R e p ro d u c tiv e S y ste m T he p ro ta n d ro u s h e r m a p h ro d ite g land is c o m p a c t, i r r e g u l a r in sh a p e , and is em b e d d e d in the d ig e stiv e g lan d . T h is gland is a r a c e m o se gland c o n s is tin g of n u m e ro u s a c in i, e a c h of w hich co n tain s m a le and fe m a le c e lls , w h ich , w hen r ip e , a r e d is c h a rg e d into the c a v ity of th e a c in u s. T h e d u c tu le s of v a r io u s a c in i u n ite into the h e r m a p h ro d ite d u c t ( F ig u r e s 42 and 43). T h e s p e r m a r e p ro d u c e d in g ro u p s o r c l u s t e r s on the in te r n a l s u rfa c e of the g land and a d h e re by th e i r h e a d s . T h e y a r e of the u s u a l e lo n g a te d type c o m m o n am o n g the m o llu s c s . T h e head of the m a tu r e s p e r m is n a r ro w and sin u o u s, its t a il v e r y long (about 150 m i c r o n s ) and s le n d e r . T h e o u te r p o rtio n of the gland is filled w ith o o c y te s , w ith d is tin c t n u c le i and n u c le o li in v a r io u s s ta g e s of d e v e lo p m e n t. T he young o vocyte h a s g r a n u la r c y to p la s m sta in in g d a rk ly . T h e n u c le u s o r g e r m in a l v e s ic le is v e r y la rg e and c l e a r e x c e p t fo r 44 c h ro m a tin e le m e n ts s c a tte r e d about. T he p ro m in e n t d e e p ly sta in in g n u c le o lu s is s p h e r ic a l in o u tlin e . T h e m a tu re egg i n c r e a s e s v e r y m u c h in s iz e to about 136 m ic r o n s . F ood m a t e r ia l is d e p o s ite d in th e c y to p la s m in the fo rm of la r g e yolk s p h e r e s w hich s ta in only w ith the b r ig h t t r io s in s ta in ( F ig u r e 45). T he co n v o lu ted h e r m a p h ro d ite d u ct lie s w ith in and e x te n d s f o r w a rd fro m the rig h t m a r g in of the liv e r to the a n t e r o - v e n t r a l sid e of th e a c c e s s o r y gland m a s s . T h e d u ct, on tu rn in g d o r s a lly o v e r the g lan d m a s s a t the le v e l of the a lb u m e n gland, s tr a ig h te n s and c o n s t r i c t s su d d en ly fo r a s h o r t d is ta n c e , th en w id en s ag ain . T h is p o rtio n of the g e n ita l du ct loops a ro u n d the s e m in a l r e c e p ta c le . Im m e d ia te ly a f te r jo in in g th re e s h o r t d u c ts fro m the s e m in a l r e c e p ta c le , a lb u m e n gland, and the co n v o lu ted p o rtio n of the m u c o u s gland r e s p e c tiv e ly , the d u c t e n te r s the m a s s and its c o u r s e can no lo n g e r be tr a c e d in s u rfa c e v iew . B elow the liv e r in th e p o s te r i o r body c a v ity lie s the g e n ita l gland m a s s . T he s e m in a l r e c e p ta c le is a blind s a c , w hich, w ith the a lb u m e n gland, lie s on the left lobe of th e m u c o u s gland and o c c u p ie s th e c a v ity of the h e m is p h e r ic a l loop fo rm e d by the h e r m a p h ro d ite d u ct. Its s ta lk o r d u ct o p en s into the h e r m a p h ro d ite d u ct, at the point w h e re the o th e r two d u c ts of th e a c c e s s o r y g lan d s jo in the h e r m a p h ro d ite duct. T he a lb u m e n gland w hich lie s a n te r io r to the s e m in a l r e c e p t a c le on the tip of th e le ft lobe of the m u c o u s gland is g r e e n is h o r 45 y e llo w ish in c o lo r and f o r m s a c o n tr a s t to the w h ite n e s s of the m u c o u s g lan d . Its s h o r t d u ct op en s into the h e r m a p h ro d ite d u ct b etw e e n the o p en in g s of the d u c ts le a d in g fro m th e s e m in a l re c e p ta c le and the m u c o u s g lan d . T h e c o n sp ic u o u s la rg e m u c o u s g land is b ilo b ed , th e le ft lobe b ein g l a r g e r th an the r ig h t lobe. T he s u rfa c e of the tr a n s lu c e n t m u c o u s gland a p p e a r s t r a n s v e r s e l y s tr ip e d ow ing to the h ig h ly folded w all. F o r m in g the a n te r io r v e n tr a l p o rtio n of the left lobe is a c o n vo lu ted p o rtio n w ith one end jo in in g the h e r m a p h ro d ite d u ct ju s t b e fo re it e n t e r s th e gland m a s s . T he o th e r end su d d en ly e n la r g e s , op en in g into the m u c o u s gland, w hich w ith the rig h t lobe d is c h a r g e s into the b a s e of the la s t s e c tio n of the h e r m a p h ro d ite d u ct. A ris in g fro m the r ig h t v e n tr a l sid e of th e g e n ita l m a s s and a f te r a few c o n v o lu tio n s, the h e r m a p h ro d ite d u c t m e e ts a s le n d e r s p e r m a th e c a l d u ct, to fo rm the g e n ita l v e s tib u le . T h e co m m o n g e n ita l opening is s itu a te d on th e r ig h t sid e of th e body. F r o m th e la s t s e c tio n of the h e r m a p h ro d ite d u ct, the s p e r m a th e c a l d u ct lo o p s o v e r the co iled p a r t of the h e rm a p h ro d ite d u ct and r u n s fo rw a rd to the s p e r m a th e c a , w h ich is a th in -w a lle d sa c fille d w ith b ro w n ish flu id . T h e s p e r m a th e c a lie s below the p e r ic a r d iu m , to w hich it is a tta c h e d by c o n n e c tiv e tis s u e . F r o m the g e n ita l opening th e s e m in a l g ro o v e e x te n d s v e n tr a lly to the rig h t rh in o p h o re . A t the a n t e r i o r , v e n tr a l end of th e rh in o p h o re . 46 the g ro o v e p a s s e s th ro u g h the m a le opening. W ithin the p e n ia l sh e a th the g ro o v e p a s s e s d o r s a l to the b a s e of the p e n ia l p a p illa . T h e h is to lo g ic a l stu d y show s th a t the h e r m a p h ro d ite d u c t h as five d iv isio n s : 1. T he f i r s t d iv isio n e m e r g e s fro m the h e r m a p h ro d ite gland a s a w id en in g co n v o lu ted d u ct c o n s is tin g of an in n e r la y e r of c ilia te d cu b o id a l e p ith e liu m and an o u te r la y e r of thin c i r c u l a r m u s c le . T he c y to p la sm of the e p ith e lia l c e ll a p p e a r s p e r ip h e r a lly . T he c e n tr a lly lo c a te d n u c le u s , ea c h w ith a s m a ll n u c le o lu s, is s p h e r ic a l o r i r r e g u l a r in o u tlin e. T he ev e n ly c ilia te d e p ith e liu m r e s t s on a th in b a s e m e n t m e m b ra n e u n d e rlin e d by a la y e r of th in c i r c u l a r m u s c le . In the s e c tio n s of a ll the s n a ils in th is stu d y , th is p o rtio n of the d u c t is u s u a lly d e n s e ly packed w ith s p e r m w hich alw ay s o b s c u re the tis s u e of the d u ct ( F ig u re 51). 2. T he s m a lle s t p o rtio n , th e seco n d , w hich ru n s a c r o s s th e fa ce of the a lb u m e n gland and loops a ro u n d th e s e m in a l r e c e p ta c le , is s tro n g ly c ilia te d . T he low c o lu m n a r e p i th e lia l c e ll, w ith its c e n tr a lly lo c ate d o v al n u c le u s , show s in tr a c e llu la r f ib r illa e (F ig u re 52), w hich g ra d u a lly d i s a p p e a r p o s te r io r ly . In the p o s te r io r p o rtio n of the d u ct, the e p ith e lia l c e ll is h ig h ly v a c u o la te d and the n u c le u s is at the d is ta l end. U su a lly s p e r m a r e found h e re and in the 47 a n t e r i o r p o rtio n of th e th ird d iv isio n of th e h e rm a p h ro d ite d u c t. T he p o s te r io r lim it of th is p o rtio n of the d u ct show s a g ra d u a l tr a n s itio n fro m a s im p le c ilia te d e p ith e liu m to a g la n d u la r e p ith e liu m of th e w id en ed th ird d iv isio n . 3. T h e th ird d iv isio n p a s s e s to th e b a s e of the a lb u m e n gland. H alf of its w a ll is lined w ith h ig h ly c ilia te d low cu b o id al c e lls w ith o v al o r r a t h e r elo n g a te d n u c le i lying t r a n s v e r s e ly . T h e o th e r h a lf is c o m p o se d of la r g e , d eep ly s ta in in g gland c e lls and w e d g e -s h a p e d c ilia te d e p ith e lia l c e lls . E a c h gland c e ll h a s a s m a ll ro u n d n u c le u s and c o n ta in s n u m e ro u s d a rk ly s ta in in g s e c r e tio n d r o p le ts (F ig u re 53). T h is p o rtio n of the d u ct en d s a t a point w h e re the th r e e d u c ts of the a c c e s s o r y g lan d s jo in . 4. The fo u rth s e c tio n b e g in s w ith th e opening of the w inding m u c o u s gland d u ct and en d s a t the point w h e re it le a v e s the g land m a s s . A fte r jo in in g the d u c ts of the a c c e s s o r y g la n d s, th is d iv isio n e n te r s the gland m a s s im m e d ia te ly and e n la r g e s to fo rm a la rg e th in -w a lle d c h a m b e r lying v e n tr a l to th e m u c o u s gland. H alf of its w a ll th a t c o n n e c ts the m u c o u s gland is lin ed w ith s tro n g ly c ilia te d e p ith e liu m , th e co m p o n en t c e lls of w hich a r e of u n ifo rm h e ig h ts, e a c h w ith an o v a l o r s p h e r ic a l d is ta lly lo c a te d n u c le u s . T he c y to p la s m above th e n u c le u s is f ib r i l l a r and p ro x im a lly is 48 h ig h ly v a c u o la te d . T he e p ith e liu m of the o th e r h a lf c o n s i s t s of c e lls v a ry in g in a p p e a ra n c e and s iz e fro m low cu b o id a l to ta ll c o lu m n a r fo rm . T h e m o s t p len tifu l c e lls a r e c lu b -s h a p e d gland c e lls co n ta in in g c e n tr a lly lo c a te d la rg e oval n u c le i ( F ig u r e 54, H D FG ). T h e seco n d type of gland c e ll co n ta in in g ro u n d g r a n u la r n u c le i is le s s p r e v a le n t and fille d w ith a c id o p h ilic s e c r e tio n d r o p le ts s ta in in g pink w ith tr i o s i n (F ig u re 54, H D FG '). S m a ll c ilia te d c e lls w ith s p h e r ic a l n u c le i a r e w edged b e tw e e n th e se gland c e lls and i n t e r s p e r s e d w ith m u c o u s c e lls . T h e g la n d u la r e p i th e lia l c e lls b e c o m e s h o r t e r and g ra d u a lly r e p la c e the c ilia te d e p ith e liu m to w a rd the lo w e r end of the d u ct. A th in la y e r of m u s c le c o a ts the h e r m a p h ro d ite d u ct th ro u g h out th is p o rtio n of the d u ct. 5. T he la s t s e c tio n of the h e r m a p h ro d ite d u c t h a s a th ick o u te r c i r c u l a r m u s c le la y e r and a c ilia te d in n e r la y e r w hich is c o m p o se d of c e lls of v a ry in g h e ig h ts w ith b a s a l n u c le i. F r o m th is d u ct, a f te r re c e iv in g the s p e r m a th e c a l d u ct a n te r io r ly , the v e s tib u le e x te n d s to the e x t e r i o r opening, th e g e n ita l p o re . A c c e s s o r y G lan d s S e m in a l r e c e p t a c l e . T h e e p ith e liu m of the s e m in a l re c e p ta c le 49 is c o m p o se d of one c e ll type w hich m ay v a r y in s iz e fro m c u b o id a l to c o lu m n a r c e lls . C o a r s e g r a n u la r m a t e r ia l is s p re a d in the p e r ip h e r y of th e n u c le u s w hich is c e n tr a lly lo c a te d and o v al in o u tlin e . T he s e m in a l r e c e p ta c le is fille d w ith s p e r m w ith th e ir h e a d s fa ste n e d to its w all v e r tic a lly . T h e c ilia of the e p ith e lia l c e lls o b s e rv e d n e a r the s ta lk of the s e m in a l r e c e p ta c le have not b e e n tr a c e d f u r th e r s in c e the d e n s e ly p ack ed s p e r m o b s c u re the s u rf a c e of the e p ith e liu m . T he e p i th e liu m r e s t s upon a th in b a s e m e n t m e m b ra n e b e n e a th w h ic h is a m u s c u la r la y e r (F ig u r e 47). T h e e p ith e liu m of the d u c t of th e s e m in a l r e c e p ta c le is m a d e up of c ilia te d c o lu m n a r c e lls w ith e lo n g a te d n u cle i; i n t e r s p e r s e d a r e la rg e glan d c e lls of tw o ty p e s. T h e y a r e c e lls w ith l a r g e r s p h e r ic a l b a s a l n u c le i in pink c o lo r ( F ig u r e 48, S D G ), and p u rp le sta in in g c e lls w ith s m a ll s p h e r ic a l n u c le i lo c a te d in v a ry in g p o s itio n s (F ig u r e 48, SDG'). B e n e a th the e p ith e liu m is a la y e r of c o n n e c tiv e tis s u e in w hich i r r e g u l a r l y a r r a n g e d m u s c le f ib e r s a r e d ev elo p ed . A lb u m en g la n d . T h e w a ll of the a lb u m e n gland is th ro w n into lo o se fo ld s. T h e e p ith e liu m is c o m p o se d of h e a v y c o lu m n a r c e lls c o n ta in in g la r g e a c id o p h ilic s e c r e tin g d r o p le ts . T he la rg e i r r e g u l a r l y sh a p e d n u c le i a r e g r a n u la r and b a s a l in p o sitio n . N a rro w w e d g e - sh a p e d c ilia te d c e lls , e a c h w ith an o v a l o r e lo n g ated n u c le u s c o n tain in g a s m a ll n u c le o lu s, a r e w edged b e tw e e n th e gland c e lls . It is d iffic u lt 50 to tr a c e the c ilia of the w e d g e -sh a p e d c e ll in the gland b e c a u s e of the s e c r e tio n d r o p le ts th a t a r e d is c h a rg e d in to th e lu m e n . H o w e v e r, at th e lo w e r end, n e a r the e n tra n c e of th e a lb u m e n d u ct, the e p ith e liu m is e v en ly c o v e re d by s h o r t c ilia . T he c o n n e c tiv e ti s s u e s u n d e rly in g the e p ith e liu m and a ro u n d th e e n tir e gland a r e th in and d e lic a te (F ig u re 50). T h e e p ith e liu m of th e a lb u m e n gland d u ct is s im i l a r to th a t of the h e r m a p h ro d ite d u c t's fo u rth d iv isio n . T he tr a n s itio n s of c e ll ty p e s b etw een th e s e m in a l re c e p ta c le and its duct; the a lb u m e n gland and its duct; and th e m u c o u s gland and the h e r m a p h ro d ite d u ct a r e a b ru p t. F e m a le m u c o u s g la n d . T he w a lls of th e m u c o u s gland a r e th ro w n into t r a n s v e r s e folds w hich give the gland a t r a n s v e r s e l y s tr ip e d a p p e a ra n c e . The lu m en is a lm o s t o b lite ra te d by th e folds of the w all, e x c e p t a t the point of the ju n ctio n w ith the h e r m a p h ro d ite d u c t. T h e e p ith e liu m is c o m p o se d of la rg e c o lu m n a r c e lls , w hich a r e fille d w ith m u c o u s s e c r e tio n s , and w e d g e -sh a p e d c ilia te d c e lls . T he o u tlin e s of th e s e gland c e lls a r e fain t, and the i r r e g u l a r sh a p e d n u c le i a r e b a s a l. T h e s e c e lls a r e v e r y r e g u la r ly a r r a n g e d upon a thin b a s e m e n t m e m b ra n e . In the m id d le re g io n of the gland, the c ilia te d c e lls a r e s m a ll and o b s c u re . T h e ir o v al o r elo n g a te d n u c le i a r e p laced d is ta lly in th e c y to p la sm ( F ig u re 46). A thin la y e r of c i r c u l a r m u s c le c o v e r s th e gland. T h e co n v o lu ted p o rtio n of the m u c o u s gland h a s an 51 e p ith e liu m s i m i l a r to th a t of th e u p p e r re g io n of the m u c o u s gland e x c e p t th a t th e c e lls a r e s m a l l e r and have m o re a ffin ity fo r the h e m a to x y lin s ta in , and the c ilia te d c e lls a re m o re n u m e ro u s . S p e r m a th e c a . T h e s p e r m a th e c a is a la r g e th in -w a lled s p h e r ic a l s a c . Its e p ith e liu m is c o m p o se d of ta ll c o lu m n a r c e lls e a c h w ith a la r g e c e n tr a lly lo c a te d o v al n u c le u s w hich c o n ta in s c o a r s e g ra n u le s . Above the n u c le u s the c y to p la s m is v a c u o la te d , p ro x im a lly a m o e b o - c y te s a r e found in the c y to p la sm . T he o u tlin e s of th e s e c e lls a r e fain t. B e n e a th th e e p ith e lia l la y e r is a la y e r of c o n n e ctiv e tis s u e in w hich i r r e g u l a r l y a r r a n g e d m u s c le f ib e r s a r e d is p e r s e d ( F ig u r e 49). The v e s ic le u s u a lly c o n ta in s a m a s s of b ro w n ish w a ste m a t t e r ( F ig u re 9). T he long s p e r m a th e c a l d u c t is lined by c ilia te d e p ith e liu m , b e n e a th w hich is an in n e r c o n n e c tiv e tis s u e la y e r and an o u te r c i r c u l a r m u s c le la y e r . In the u p p e r p o rtio n of the d u ct, the c e lls of the e p ith e liu m a re c o lu m n a r and have b a s a l e lo n g a te d n u c le i. In the lo w e r re g io n , the e p ith e lia l c e lls b e c o m e s h o r t e r and have ov al n u c le i. M ale O rg a n s ( F ig u r e s 42 and 44) P r o s t a t e G la n d . The p r o s ta te gland is a lig h t y e llo w ish c o lo re d o v a l-s h a p e d m a s s on the left sid e of the h ead re g io n . T h e e p ith e liu m of the p r o s ta te gland is th ro w n into d eep lo n g itu d in al fo ld s. T h e c o lu m n a r c ilia te d c e lls have e lo n g a te d o r ov al n u c le i w ith m a r k e d 52 n u c le o li and c h ro m a tin m a t e r ia l ly in g to w a rd the c e n te r of th e f ib r illa r c y to p la s m . T he s u b -e p ith e lia l g land c e lls of the p r o s ta te a r e g ro u p e d in c l u s t e r s . E a c h gland c e ll h a s a la r g e , ro u n d , b a s a l, d a r k ly s ta i n ing n u c le u s . T he c y to p la sm is p ack ed w ith g r a n u le s . B e tw e e n th e s e g land c e lls a r e w edged s m a ll c e lls w ith d a r k ly s ta in in g n u c le i. C o n n e c tiv e tis s u e is d e v e lo p e d b e tw e e n the e p ith e liu m and th e s u b - e p ith e lia l gland c e lls ; a th in la y e r of c i r c u l a r m u s c le c o a ts th e g land (F ig u r e 56). F r o m the n otch on the rig h t sid e of the p r o s ta te a r i s e s the p r o s ta tic d u c t, the e p ith e lia l lin in g of w h ich is s i m i l a r to th at o f p r o s ta te but w ith s m a l l e r c e lls . A fte r le a v in g th e gland the e p ith e liu m b e c o m e s fla t and the c ilia d is a p p e a r . T h e lu m en of the p r o s ta tic d u ct is fo u r-fo ld e d ( F ig u r e 8). It c o n s is ts of th r e e la y e r s : an in n e r e p i th e lia l lin in g c o n s is tin g of fla t c e lls w ith e lo n g a te d n u c le i, th e s e c e lls b e c o m in g t a l l e r in the tro u g h of th e fo ld s; a m id d le la y e r c o n ta in in g la r g e o v al c e lls w ith i r r e g u l a r sh a p e d n u c le i, p r a c tic a lly no c e ll c o n te n ts b ein g p r e s e n t in th e c e lls ; and an o u te r c i r c u l a r m u s c le la y e r . T he d is ta l end of the p r o s ta tic d u c t o p en s into the p e n ia l b u lb , w hich is e llip tic a l and th ic k ly m u s c u la r . T h e lin in g of th is p o rtio n of th is d u ct is c ilia te d c o lu m n a r e p ith e liu m . T h e se c e lls hav e b a s a l o v al n u c le i w ith p r o m in e n t n u c le o li. P e n is and p e n ia l s h e a th . T h e p r o s ta tic d u ct en d s into a h ig h ly 53 folded c a v ity of th e p e n ia l b ulb w hich is lin ed by cu b o id a l e p ith e liu m w ith i r r e g u l a r sh a p e d n u c le i w h o se n u c le o li a r e p ro m in e n t. T he p e n ial bulb c o n s is ts of an o u te r th ic k e r , c i r c u l a r m u s c le la y e r and an in n e r th in n e r, lo n g itu d in al m u s c le la y e r . T h e c i r c u l a r m u s c le la y e r ta p e r s g ra d u a lly to jo in th e p e n ia l s h e a th tis s u e and p r o je c ts a s a p en ial p a p illa into the c ilia te d and folded p e n ia l s h e a th . T h e lo n g itu d in al m u s c le la y e r f o r m s the m u s c u la r w a ll of the p e n is d is ta lly . B etw e en th e s e tw o la y e r s th e r e is a c a v ity . The u n a r m e d te r m in a tio n of th is d u c t, th e p e n is, is c o m p le te ly r e t r a c t i l e w ith in its s h e a th . T h e lu m en of the p e n is is lined by sq u a m o u s e p ith e liu m w ith i r r e g u l a r n u c lei. T h e e p ith e lia c o v e rin g th e p e n is and lining the c a v ity of the c i r c u l a r m u s c le la y e r a r e id e n tic a l. T h e p e n ia l sh e a th is a m u s c u la r c u l - d e - s a c w hose b lin d end, to w hich the p e n ia l p a p illa is a tta c h e d , is p o s te r io r . T h e w a lls of the s h e a th a r e a tta c h e d by n u m e ro u s m u s c le s to th e body w all. It is lined by c ilia te d c o lu m n a r e p ith e liu m w ith b a s a l o v al o r s lig h tly elo n g ated n u c le i. T he c ilia of the e p ith e lia l c e lls d is a p p e a r n e a r the le v el of the p e n ia l p a p illa . T h e c o n tin u a tio n of th is u n c ilia te d e p ith e liu m co ats the p e n ia l p a p illa . The c o lu m n a r c e lls of th is p o rtio n g ra d u a lly s h o rte n into c u b o id al e p ith e liu m . B e n e a th the e p ith e liu m is a n e tw o rk of lo o se c o n n e c tiv e tis s u e w ith b lood s p a c e s , f la s k - lik e , s u b -e p ith e lia l gland c e lls , and m u c o u s c e lls . T h e f la s k - lik e , s u b -e p ith e lia l gland c e lls h av e d a rk ly sta in in g la r g e s p h e r ic a l n u c le i to w a rd t h e i r b a s e s . 54 U n d e rly in g th e tis s u e is a h ea v y la y e r of i r r e g u l a r l y a r r a n g e d m u s c le f ib e r s . F r o m th e d o r s a l w a ll of the lu m e n two lo n g itu d in al fo ld s c o n ta in in g m o re blood s p a c e s h an g alo n g the e n tire length of the p e n ia l sh e a th (F ig u r e 44). On the rig h t d o r s a l s id e b e g in s a lin e a r lo n g itu d in a l g ro o v e . T h is is the s e m in a l g ro o v e , w h ich te r m in a te s c lo s e to th e b a s e of th e p e n ia l p a p illa and can be t r a c e d fo rw a rd alo n g th e r ig h t sid e of the p e n ia l s h e a th and o v e r the edge of the m a le o p ening. H e re it is co n tin u o u s w ith th e l a t e r a l s e m in a l g ro o v e on the e x t e r i o r of the body. W hen th e p e n is is th r u s t f ro m its s h e a th , the la tte r b e c o m e s e v a g in a te d . T h e s e m in a l g ro o v e is th u s s tra ig h te n e d out. F r o m the g e n ita l opening a sh a llo w c ilia te d g ro o v e , b e tw e e n the v i s c e r a l m a s s and th e r ig h t p a ra p o d iu m , r u n s fo rw a rd to th e m a le o p en in g s itu a te d a t the a n t e r i o r end of th e rig h t rh in o p h o re . Its l a t e r a l w a lls a r e fo rm e d by p ro je c tio n s of the body w a ll. T h e g ro o v e is lined by c ilia te d c u b o id a l e p ith e liu m . T h e c e lls a r e th ic k ly and ev e n ly c o v e re d by a la y e r of c ilia a r is in g fro m b a s a l g ra n u le s w hich can be s e e n v e r y c l e a r ly in s e c tio n . B e n e a th the g r a n u le s , the c y to p la s m is v a c u o la te d and lig h tly s ta in in g . A s p h e r ic a l g r a n u la r n u c le u s w ith m a rk e d n u c le o lu s is s itu a te d to w a rd the b a s e of e a c h c e ll and aro u n d the n u c le u s the c y to p la s m is v e r y c l e a r . T he tis s u e u n d e rly in g the e p ith e liu m of th e l a t e r a l w a lls is flan k ed by la r g e blood s p a c e s w hich m ig h t c lo se the g ro o v e w h ile s p e r m a r e ru n n in g th ro u g h it. IV. SUMMARY 1. A ll the s p e c im e n s of H a m in o e a v e s ic u la G ould stu d ie d w e re c o lle c te d fro m L u n a d a B ay, P a lo s V e r d e s , C a lifo rn ia , and P o in t P e r m in, San P e d r o , C a lifo rn ia . 2. T h e m o rp h o lo g y a s w e ll a s so m e of th e h is to lo g ic a l a s p e c ts of the a n im a l have b een stu d ie d . 3. T he s n a ils stu d ie d a v e ra g e 26 m m in len g th and 12 m m in g r e a t e s t d ia m e te r . 4. T h e s h e ll is f r a g ile , tr a n s lu c e n t, o v a l-s h a p e d , w ith a w ide a p e r t u r e . It a lw a y s f o r m s one and a h a lf d e x tr a l w h o rls . 5. T h e body m a y be div id ed into th r e e re g io n s : the c e p h a lic re g io n , the v i s c e r a l m a s s and the foot. T h e body c a v ity is the h e m o c o e le w hich c o n s is ts of an a n t e r i o r h e m o c o e le and a p o s te r io r h e m o c o e le w ith a “ d ia p h r a g m " b e tw e e n th e m . It is lined by a n e tw o rk of m u s c le f ib e r s . T h e tr u e co elo m is r e p r e s e n te d by th e p e r ic a r d ia l c a v ity , th e r e n a l cav ity , and the c a v ity of the gonad. T h e head b e a r s the m outh, e y e s , te n ta c le s , r h in o p h o re s , and th e m a le c o p u la to ry o rg a n . T h e v i s c e r a l m a s s is c o v e re d by the m a n tle and is c o m p o se d of th e d ig e s tiv e o r g a n s , the liv e r , and th e r e p r o d u c tiv e o rg a n s w ith th e ir a c c e s s o r y g la n d s. T h e p a llia i c a v ity ly in g d o r s a l to the v i s c e r a l m a s s c o n ta in s the sin g le 55 56 c te n id iu m . T h e k id n ey , th e g e n ita l g la n d s, and the c y a n o - p h ilo u s g lan d s d is c h a rg e into th is c av ity . 6. T he foot is an e lo n g ated fla tte n e d m u s c u la r s tr u c t u r e w hose l a t e r a l e x p a n sio n s fo rm th e p a ra p o d ia . An in fr a p a llia l lobe e x te n d s p o s te r io r ly a s a “ t a i l . " T he foot and m u s c u la r body a r e of a spongy n a tu r e w ith ab u n d an t blood lac u n a e and m u s c le f ib e r s . A ll m u s c le s of H a m in o e a v e s ic u la a r e sm o o th . 7. T h e d ig e s tiv e s y s te m is c o m p o se d of th e follow ing m o rp h o lo g ic a lly d is tin c t p a r ts : m o u th , b u c c a l m a s s , e so p h a g u s, a n t e r i o r and p o s te r i o r c r o p s , g iz z a r d , s to m a c h , in te s tin e , r e c tu m , s a liv a r y g la n d s, and the liv e r . T h e m o u th is a v e r tic a l s lit s itu a te d in the g ro o v e b e tw e e n the h ead and the foot. T h e b u c c a l m a s s c o n ta in s a p a ir of h o rn y d e n tic u la te d ja w s , and th e o d o n to p h o re a r is in g fro m th e flo o r of th e b u c c a l c a v ity and b e a r in g the r ad u la. Tw o ty p e s of te e th , c e n tr a l and l a t e r a l s a r e a r r a n g e d in a 5 0 -6 1 , 1, 50-61 f o rm u la . T h e r a d u la s a c is su p p o rte d c e n tr a lly by the c a r tila g in o u s c o llo s ty l. T he b u c c a l ca v ity , e x c e p t fo r th e p o s te r i o r p a r t of the d o r s a l p h a ry n g e a l c a n a l w hich is c o v e re d by c ilia te d e p ith e liu m , is lined th ro u g h o u t by a c u tic u la te d e p ith e liu m . T h e e so p h a g u s is a s le n d e r tube of c o lu m n a r e p ith e liu m . It b e a r s a d o r s a l e s o p h a g e a l 57 d iv e rtic u lu m . T h e g iz z a r d c o n ta in s th re e c h itin o u s p la te s w hich b e a r te e th , th r e e g iz z a r d te e th s itu a te d b e tw e e n the p la te s , and th r e e th in -w a lle d g la n d u la r g iz z a r d d iv e r tic u la . T he w a lls of the g iz z a r d a r e highly m u s c u la r . T h e s to m a c h is a U -s h a p e d , th in -w a lle d s a c e m b e d d e d in th e liv e r; its c ilia te d c o lu m n a r e p ith e liu m c o n s is ts of d iff e r e n t ty p e s of g land c e lls . T h e in te s tin e is lined th ro u g h o u t by c ilia te d c o lu m n a r e p ith e liu m w ith m u c o u s and gland c e lls . 8. T h e p a ire d elo n g ate d s a liv a r y g lan d s lie alo n g e a c h sid e of the e so p h a g u s and d is c h a r g e into the p o s te r i o r d o r s a l p a r t of the b u c c a l c a v ity . T h e y c o n s is t of a n u m b e r of s m a ll tu b u le s lin ed w ith e p ith e liu m co m p o se d of c ilia te d and gland c e lls . 9. T h e liv e r o c c u p ie s the g r e a t e s t p a r t of the h e m o c o e le . It c o n s is ts of n u m e ro u s tu b u le s bound to g e th e r by c o n n e c tiv e tis s u e . T h e in n e r lin in g of e a c h tu b u le is c o m p o se d of e x c r e tin g and d ig e s tiv e c e lls . 10, T h e c ir c u la to r y s y s te m c o n s is ts of a two c h a m b e re d h e a r t, a r t e r i e s , v e in s and la c u n a e . T h e re is no e n d o th e lia l tissu e lining th e v e n tr ic u la r and a u r ic u la r c a v itie s so th a t the m u s c le f ib e r s of th e h e a r t a r e d ir e c tly b a th e d in th e blood. 11. T he p in n ated c te n id iu m lie s a c r o s s th e ro o f of th e p a llia i c a v ity . E a c h pinnule is fo rm e d by tw o la y e r s of e p ith e lia 58 w ith a c e n t r a l s p a c e b e tw e e n th e m . 12. T h e s o m e w h a t tria n g le sh ap ed k id n ey is s itu a te d o v e r the rig h t s id e of th e liv e r. It is c o m p o se d of a s e r i e s of p a r a lle l la m e lla e c o n s is tin g of g la n d u la r c e lls w ith la rg e v a c u o le s , 13. T h e c e n t r a l n e rv o u s s y s te m c o n s is ts of th re e p a ir s of m a j o r g a n g lia, the c e r e b r a l, th e p e d a l and th e p le u r a l g a n g lia . T h e y a r e linked to e a c h o th e r by c o m m i s s u r e s , fo rm in g th e n e rv e rin g . T h e n e rv o u s s y s te m is sh e a th e d in a th in c o n n e c tiv e tis s u e en v elo p e , in w hich n u m e ro u s blood s in u s e s a r e lo c a te d . 14. T h e s e n s e o rg a n s a r e th e p a ir e d e y e s , p a ire d rh in o p h o r e s , p a ire d o to c y s ts , and a s in g le o s p h ra d iu m . T he e y e s a r e s itu a te d n e a r the in n e r b a s e s of th e a u r ic u la te d te n ta c le s . E a c h eye c o n s is ts of the c o rn e a , r e tin a , le n s, optic c a p su le and optic n e r v e . T h e s m a ll c i r c u l a r o s p h ra d iu m is a w a te r ta s tin g o rg a n lo c a te d im m e d ia te ly a n t e r i o r to the a n t e r i o r a tta c h m e n t of the c te n id iu m , c o n s is tin g of no n - c ilia te d c o lu m n a r s e n s o r y e p ith e liu m . T h e o to c y s ts a r e s itu a te d on th e p e d a l g a n g lia and c o n ta in m an y o v al sh a p e d o to lith s. T h e rh in o p h o r e s , th e o lfa c to ry o r g a n s , a r e yello w p e c tin a te s e n s o r y s t r u c t u r e s . T h e y a r e s itu a te d on e a c h sid e of the a n t e r i o r body w a ll b etw e en the c e p h a lic 59 s h ie ld and the foot, 15. H a m in o e a v e s ic u la is h e r m a p h ro d itic . T he r e p ro d u c tiv e o rg a n s c o n s is t of a h e r m a p h ro d ite g lan d , a c o m m o n g e n ita l d u c t, fe m a le a c c e s s o r y g la n d s, r e s e r v o i r s f o r th e m a le e le m e n ts , p r o s ta te g lan d , and a m a le c o p u la to ry o rg a n o r p e n is. T h e o v o te s tis is a r a c e m o s e gland c o n s is tin g of n u m e ro u s a c in i e a c h of w hich c o n ta in s m a le and fe m a le c e lls . T he fe m a le a c c e s s o r y g lan d s a r e th e a lb u m e n gland and the m u c o u s g lan d . T he r e s e r v o i r s f o r the m a le e l e m e n t a r e th e s e m in a l r e c e p ta c le and s p e r m a th e c a . A P P E N D I X E S A P P E N D IX A LIST O F A B BREV IA TIO N S A P P E N D IX A LIST O F A B BREV IA TIO N S A an u s AA a n te r io r a o r t a ABGC gland c e ll of a lb u m e n gland AG a lb u m e n gland AM a m o e b o c y te AN a u d ito ry n e rv e AO co m m o n a o r ta A P N a n t e r i o r p e d a l n e rv e AU a u r ic le AV a ffe re n t v e s s e l B b u c c a l m a s s BC b u c c a l c a v ity BG b u c c a l g an g lio n BM b a s e m e n t m e m b ra n e BON b r a n c h io - o s p h r a d ia l n e rv e B P C b ra n c h io - p a r i e t a l c o m m is s u r e BR G b r a n c h ia l g an g lio n BS blood sp a c e BU M b u c c a l m u s c le BV b r a n c h ia l v ein BW body w a ll C c e n t r a l tooth CC c ilia te d e p ith e lia l c e ll CD c te n id iu m CDN c te n id iu m n e r v e C E c ilia te d e p ith e liu m C E C c e r e b r a l c o m m is s u r e C E C ' s u b c e r e b r a l c o m m is s u r e C E G c u t edge of g a s tr i c lin in g of g iz z a rd C E M c u t edge of m a n tle C E W cu t edge of b u c c a l w a ll CG c e r e b r a l g an g lio n C L c ilia CM c i r c u l a r m u s c le CN c e r e b r a l n e rv e to v e n tr a l s id e of m o u th re g io n CO c o r n e a C P C c e r e b r o - p e d a l c o m m is s u r e 62 63 CR a n t e r i o r c ro p C R ' p o s te r i o r c ro p C T c o n n e c tiv e tis s u e CY c y a n o p h ilo u s gland DC d ig e s tiv e c e ll D F d o r s a l l a t e r a l fold D P C d o r s a l p h a ry n g e a l c a n a l E eye EC e x c r e tin g c e ll ED e s o p h a g e a l d iv e rtic u lu m E E e x p a n sio n e p ic o c h le a ir e E E ' cu t edge of e x p a n sio n e p ic o c h le a ire E L e p id e r m a l la y e r E M e x c r e to r y m a t t e r E P e p ith e liu m ES e so p h a g u s E V e f fe r e n t v e s s e l F foot P C fo llic le c e ll F M fe m a le m u c o u s gland F M ' co n v o lu ted p o rtio n of fe m a le m u c o u s gland FM C m u c o u s c e ll of fe m a le m u c o u s gland F T fib ro u s tis s u e G g iz z a r d GA g e n ita l a r t e r y G A' g e n ita l a r t e r y (to the lo w e r p a r t of g e n ita l d u ct) GC gland c e ll GD g iz z a r d d iv e r tic u lu m G EA g a s tr o - e s o p h a g e a l a r t e r y GG g e n ita l g an g lio n GN g e n ita l n e rv e GO g e n ita l p o re G P g iz z a r d p late GR g ro o v e GV g e n ita l v e s tib u le H h e a d HA h e p a tic a r t e r y HC h e m o c o e le H D l f i r s t d iv isio n of h e r m a p h ro d ite d u ct H D 2 s e c o n d d iv isio n of h e r m a p h ro d ite d u ct H D 3 th ir d d iv isio n of h e r m a p h ro d ite duct HD4 fo u rth d iv isio n of h e r m a p h ro d ite du ct H D 5 fifth d iv isio n of h e r m a p h ro d ite d u ct H D FG g lan d c e ll of HD4 H D FG ' se c o n d type of gland c e ll of HD4 64 H D L lu m e n of h e r m a p h ro d ite d u c t HDTG g land c e ll of H D 3 HED h e p a tic d u ct HG h e r m a p h r o d ite gland HO opening of h e p a tic d u c t I in te s tin e IGC g lan d c e ll of in te s tin e IGC' se c o n d ty p e of gland c e ll of in te s tin e IG C" th ir d ty p e of gland c e ll of in te s tin e IP in f r a p a llia l lobe IZ in n e r zone J jaw K k id n ey L le n s L I f i r s t l a t e r a l tooth L2 sec o n d l a t e r a l tooth LIO te n th l a t e r a l tooth L30 th ir tie th l a t e r a l tooth LA la m e lla L F lo n g itu d in a l fold LN la b ia l n e rv e L T liv e r tu b u le LU lu m e n LV liv e r M m o u th MC m u c o u s c e ll M CN m u s c u lo -c o n n e c tiv e n e tw o rk M F m u s c le f ib e r s MN m a n tle n e rv e MO m a le opening M PN m id d le p e d a l n e rv e MS c a r d ia c m u s c le N n u c le u s N F M n u c le u s of m u c o u s c e ll NG n e u ro g lia NGC n u c le u s of gland c e ll NN n u c le u s of n e u ro n NOV n u c le u s of ovum NU n e u ro n NWC n u c le u s of w e d g e -sh a p e d c e ll OB o d o n to b la st OD o d o n to p h o re O L o to lith ON o p tic n e rv e OS o s p h ra d iu m 65 OSG o s p h ra d ia l ganglion OSN o s p h r a d ia l n e rv e O T o to c y st OV ovum O Z o u te r zone P p en is P A p o s te r i o r a o r ta PA G p a llia i c a e c u m PA G p a r ie ta l g an g lio n P A N p a r a p e d a l n e rv e P B p e n ia l bulb P C p e d al c o m m is s u r e P C ' p a r a p e d a l c o m m is s u r e P C C c e r e b r o - p l e u r a l c o m m is s u r e P D p r o s ta tic d u ct PD G p e d a l g an g lio n P E p e r ic a r d iu m P G p r o s ta te gland P G C p e d a l gland PG D p e d a l gland d u ct P I p e n ia l p a p illa P L G r ig h t p le u r a l g an g lio n P L G ' le ft p le u r a l g an g lio n P P p a ra p o d iu m P P G p le u r o -p e d a l c o m m is s u r e P P N p o s te r io r p e d a l n e rv e P P N ' p o s te r io r p e d a l n e rv e P P N " p o s te r i o r p e d a l n e rv e P S p e n ia l s h e a th P S ' cu t edge of p e n ia l sh e a th P S P p a r a s itic s p o ro z o a n P Z p ig m e n t zone R r e c tu m RA ra d u la RC ra d u la c o llo s ty l RH rh in o p h o re RN r a d u l a r n e rv e R P r e n a l p o re R P N rh in o p h o re n e rv e RS r a d u la sa c RV r e n a l v e in S s to m a c h S' c u t edge of s to m a c h SAG s a liv a r y gland SAGG gland c e ll of s a liv a r y gland 66 SAGC' se c o n d type of g land c e ll of s a liv a r y gland SBG s u b in te s tin a l g an g lio n SC s e n s o r y c e ll SDG g lan d c e ll of the d u c t of s e m in a l r e c e p ta c le SDG' se c o n d type of gland c e ll of th e d u c t of s e m in a l r e c e p ta c le SDGC gland c e ll of the d u c t of s a liv a r y gland SG s e m in a l g ro o v e SGC g land c e ll of s to m a c h SGC' se c o n d type of gland c e ll of s to m a c h SGD s a liv a r y g lan d d u ct SLV s e m i - l u n a r v alv e SN s a liv a r y n e rv e SP s p e rm a to z o o n SR s e m in a l r e c e p ta c le ST s p e r m a th e c a STC s to m a to g a s tr ic c o m m is s u r e STD s p e r m a th e c a l d u ct STN s to m a to g a s tr ic n e rv e T to o th TA te n ta c le T N te n ta c le n e rv e V v e n tr ic le VA v a c u o le VC r ig h t v i s c e r a l c o m m is s u r e V C' le ft v i s c e r a l c o m m is s u r e VG v i s c e r a l g anglion VN v i s c e r a l n e rv e A P P E N D IX B P L A T E S P L A T E I S H E L L AND SNAIL F ig u r e 1. D o r s a l view of the e n tir e s h e ll. X 2.5 F ig u r e 2. V e n tr a l view of the e n tir e s h e ll. X 2.4 F ig u r e 3. D o r s a l view of th e living s n a il. T h e a n im a l is not fu lly e x te n d e d . X 3 F ig u r e 4. D ia g r a m of the v e n tr a l view of a s p e c im e n . X 2.5 69 PLATE I 1 ê £ à ê & T A P L A T E II P A L L IA L C O M P L E X AND C IR C U LA TO R Y SYSTEM F ig u r e 5. D o r s a l view of the p a llia i c o m p le x . T h e m a n tle , c y a n o p h ilo u s g la n d s, and p a r t of th e p e r ic a r d iu m h av e b e e n d is s e c te d aw ay. T h e c te n id iu m is m o v ed slig h tly p o s te r io r . X 4 F ig u r e 6. D ia g r a m of th e h e a r t and th e blood v e s s e l s . X 11 F ig u re 7. T he v e n tr ic le show ing th e tw o s e m i - l u n a r v a lv e s b e tw e e n th e v e n tr ic le and th e a u r ic le . X 11 PLATE II 71 SLV___ LV RP AO PE EE - J CEM I SG EV I PP I RH GO PAC OS Ap __GEA P L A T E III SEC TIO N S O F C E P H A L IC AND P A L L IA L REG IO N S F ig u r e 8. H o riz o n ta l s e c tio n th ro u g h th e a n t e r i o r re g io n of the a n im a l show ing the v a r io u s o r g a n s . F ig u r e 9. H o riz o n ta l s e c tio n th ro u g h th e p o s te r io r re g io n of th e a n im a l show ing the v i s c e r a l m a s s , c te n id iu m , h e a r t, s p e r m a th e c a , c y a n o p h ilo u s g lan d , and th e k id n ey . PLATE 73 6 P _ ^ _ g 1 ^ PS -SAG $ CR___ IMM 8 S „ _ 0 S 6 IM M P L A T E IV SECTIO N S O F M A N TLE SKIRT AND P E D A L TISSUE F ig u re 10. S ectio n of the m a n tle s k ir t show ing the h is to lo g ic a l s tr u c t u r e . F ig u r e 11. S ectio n th ro u g h the p e d a l tis s u e show ing the p ed a l gland and the c ilia te d e p ith e liu m . 75 PLATE IV \ / * p « K ^ ' ■ * # # $ ------ NGC M F__ % _ > - 6* » J _l 4a a 0.04M M 10 CE___ s f •*; ,'* \é A 3 P G D -^ ^ ~ '^ -r PGC y , * 0.0 4 M M P L A T E V D IG EST IV E SY STEM F ig u r e 12. D o r s a l view of th e d ig e s tiv e s y s te m . T h e v i s c e r a l m a s s h a s b e e n tu rn e d slig h tly to th e r ig h t. X 8.5 F ig u r e 13. D is s e c tio n of th e s to m a c h to show the o p en in g of th e h e p a tic d u c t and th e lo n g itu d in al fo ld s of th e s to m a c h . T h e r ig h t w a ll of th e s to m a c h h a s b e e n r e m o v e d , X 8,5 PLATE V 77 SGD__ E S - __ BUM SAG -WED 12 P L A T E VI B U C C A L C O M P L E X F ig u r e 14. V e n tra l v iew of th e b u c c a l m a s s . X 13 F ig u r e 15. P o s t e r i o r view of th e b u c c a l m a s s show ing the b u c c a l g a n g lia and n e r v e s . X 13.5 F ig u r e 16. L a te r a l v iew of th e b u c c a l m a s s , p a r t of th e s u p e r f ic ia l m u s c le la y e r h a s b e e n cu t aw ay. X 13 F ig u r e 17. L a te r a l d is s e c tio n of the b u c c a l m a s s to show the o d o n to p h o re and jaw . X 13 F ig u r e 18. L a te r a l d is s e c tio n of the b u c c a l m a s s . T h e rig h t w a ll of the o d o n to p h o re h a s b e e n d is s e c te d aw ay to show the r a d u la and th e ra d u la s a c . X 13 PLATE VI 79 -STN — SN ;r-BUM RN___ CEW— : 17 P L A T E VII SECTIO N S O F B U C C A L A R E A AND RADULA SAC F ig u re 19. H o riz o n ta l s e c tio n th ro u g h the b u c c a l a r e a show ing th e ra d u la , o d o n to p h o re , and the ja w s . F ig u re 20. T r a n s v e r s e s e c tio n th ro u g h the ra d u la s a c . PLATE VII 81 . / . D P C - 0 0 ---- R A J i ^ _ IM M 19 T _ FC- O B______ 0.2MM % |S _ E P P L A T E VIII G IZZA R D AND RA D U LA T E E T H F ig u re 21. L a te r a l view of th e g iz z a rd show ing th e g iz z a r d p la te s and th e g iz z a rd d iv e r tic u la r e la tio n . X 8 F ig u re 22. A n te r io r d is s e c tio n of the g iz z a r d to show the a r r a n g e m e n t of the g iz z a rd p la te s in the g iz z a r d . T h e e s o p h a g u s and th e g iz z a rd d iv e r tic u la h av e b e e n d is s e c te d aw ay. X 7 F ig u r e 23. L a te r a l view of a sin g le g iz z a rd p la te . X 14.5 F ig u re 24. V e n tra l view of a sin g le g iz z a rd p la te . X 14.5 F ig u r e 25. D ia g r a m of r a d u l a r te e th show ing t h e i r a r r a n g e m e n t in a s in g le t r a n s v e r s e ro w . F ig u r e 26. L a te r a l view of th e th ir tie th l a t e r a l to o th . X 188 F ig u re 27. C e n tr a l to o th . X 188 F ig u re 28. L a te r a l view of th e f i r s t l a t e r a l to o th . X 188 83 PLATE VII! 23 L30 22 24 LI L2 LiO 25 26 c 27 Li 28 P L A T E IX SECTIO N S O F G IZZ A R D D IV E R T IC U L U M AND LIV E R F ig u re 29. S ectio n th ro u g h the g iz z a rd d iv e rtic u lu m . F ig u re 30. S ectio n th ro u g h th e liv e r. 85 PLATE IX i lA T' ' * t m - / ' 4 - « j s ^ ' “ « r 4 ' & _NGC A- LU-------- .A - i f 0.04MM V \ V 29 ■ ^ 4 1 GC DC----------- ' 2' \ ,AM m m ' 0.0 4 M M P L A T E X SEC TIO N S O F D IG EST IV E ORGANS, G LA N D , AND RH IN O PH O RE F ig u re 31. T r a n s v e r s e s e c tio n of p a r t of th e s to m a c h e p i th e liu m show ing v a r io u s ty p e s of gland c e lls . F ig u re 32. T r a n s v e r s e s e c tio n of p a r t of th e m id - in te s tin a l e p ith e liu m show ing v a r io u s ty p e s of gland c e lls . F ig u re 33. T r a n s v e r s e s e c tio n th ro u g h a tu b u le of th e s a liv a r y gland. F ig u r e 34. T r a n s v e r s e s e c tio n th ro u g h th e p r o x im a l p o rtio n of th e d u ct of s a liv a r y gland. S om e of the gland c e lls a r e in s e c r e tin g p h a se . F ig u re 35. T h e e p ith e liu m of the rh in o p h o re sh o w in g the s e n s o r y c e ll. PLATE X 87 SGC -----CC IGC__LL - S G C ' _M C — AM —BM -S A G C EP 80 -SA G C ' —SDGC P L A T E XI SECTIO N S O F H E A R T AND KIDNEY F ig u re 36. S ectio n th ro u g h the v e n tr ic le show ing the lo o se i r r e g u l a r l y a r r a n g e d c a r d ia c m u s c le . F ig u re 37. S ectio n th ro u g h the kidney show ing the h is to lo g ic a l s tr u c tu r e of the kidney la m e lla e . PLATE XI 89 ■ H * . m i 'i î * ' ' m" ^ »* T> *■ • ‘- , ( f • -f-*' . » r r ^ '1 % . t AM : >, T'. % ' / je %: & % » 0 . % - \ ; V PSP 0.05MM 36 • & < 5 > i # # ___ EM *• % LU O « i N-------- S 0.05MM , é . *' c 37 # P L A T E X II NERVOUS SY STEM F ig u r e 38. D o r s a l view of th e n e rv o u s s y s te m . X 11.5 F ig u r e 39. I llu s tr a tio n of the th r e e p r in c ip le g a n g lia (rig h t) and t h e i r a s s o c ia te d n e r v e s . T h e c e r e b r a l g an g lio n h a s b e e n lifte d up to show th e o to c y s t, a u d ito ry n e r v e , and th e th r e e c o m m is s u r e s c o n n e c tin g th e s e g a n g lia . X 17.5 PLATE XII 91 PPN_ PPN!______ CN___ ON— TN__> P L G -- MN____ CDN OSN GN___ — VN CEC— STC— CECL — PAN CPC PPN” PPN’ 39 P L A T E XIII SECTIO N S O F EY E AND O TO CY ST F ig u r e 40. S a g itta l s e c tio n th ro u g h th e e y e. F ig u re 41. T r a n s v e r s e s e c tio n th ro u g h the p e d al g an g lio n and th e o to c y st. PLATE XIII 93 0.16M M 4 0 ;_MCN B S___ • % * * - OT— y é A I \ V OL, I ê * PAN___ ( 0.04MM _N N FT ,_ N 6 .NU d * 41 P L A T E XIV R E P R O D U C T IV E SY STEM F ig u r e 42. D is s e c tio n f ro m the d o r s a l a s p e c t to show the r e p ro d u c tiv e s y s te m . T h e v a r io u s o rg a n s and the a c c e s s o r y g e n ita l g la n d s hav e b e e n s p re a d out fo r c la r ity . X 4 F ig u r e 43. V e n tra l view of the re p ro d u c tiv e o r g a n s . T he m a le a p p a r a tu s a r e not show n. X 6 F ig u r e 44. D is s e c tio n of th e m a le c o p u la to ry o rg a n f ro m the d o r s a l a s p e c t, show ing th e p e n is and th e s e m in a l g ro o v e . X 5.5 PLATE XIV 95 STD__ HC RH. MO PG. PS PD 86 PB ST .60 AA 6V G A ' STD HD5 FM H D I CY HG EE PP. 42 MO --H D 3 --H D 2 HDI- HG----- ___ BW __SG 43 P L A T E XV SEC TIO N S O F H E R M A P H R O D IT E GLAND AND F E M A L E MUCOUS GLAND F ig u r e 45. S ectio n th ro u g h th e v i s c e r a l m a s s of an ad u lt a n im a l show ing the h e r m a p h ro d ite gland w ith s p e r m and d e v e lo p in g e g g s , and th e liv e r tu b u le s. F ig u re 46. S e c tio n of th e fe m a le m u c o u s gland show ing the h is to lo g ic a l s t r u c t u r e . 97 PLATE XV HDI ■ . *V. ' » 7^ V , -■ / ' , . . L ---------------LT 0.17MM 45 # $ . I 1 % . i ; t LU <A , NWC - - . - C L V . V » 0.04MM * Î------------- FMC NFM 4 6 P L A T E X VI SECTIO N S O F G E N IT A L ACCESSO RY GLANDS AND H E R M A PH R O D IT E D U CT F ig u r e 47. T r a n s v e r s e s e c tio n of p a r t of the s e m in a l r e c e p t a c le e p ith e liu m . F ig u re 48. T r a n s v e r s e s e c tio n of p a r t of the d u ct of s e m in a l r e c e p ta c le to show the d iffe re n t ty p e s of gland c e lls . F ig u re 49. T r a n s v e r s e s e c tio n of p a r t of the s p e r m a th e c a e p i th e liu m . F ig u r e 50. T r a n s v e r s e s e c tio n th ro u g h p a r t of th e a lb u m e n g la n d . F ig u r e 51. T r a n s v e r s e s e c tio n of p a r t of the f i r s t d iv isio n of the h e r m a p h ro d ite d u ct. F ig u re 52. P a r t of a t r a n s v e r s e s e c tio n of the se c o n d d iv isio n of the h e r m a p h ro d ite d u ct to show the h ig h ly c ilia te d e p ith e liu m . F ig u r e 53. T r a n s v e r s e s e c tio n of the th ird d iv isio n of the h e r m a p h ro d ite d u c t to show the h is to lo g ic a l s tr u c t u r e of th is p o rtio n . H alf of its w a ll c o n s is ts of c ilia te d c e lls , and th e o th e r h alf, the g la n d u la r c e lls . F ig u r e 54. P a r t of a t r a n s v e r s e s e c tio n of the fo u rth d iv isio n of the h e r m a p h ro d ite d u c t. T h is p o rtio n is an e n la rg e d c h a m b e r , h a lf of w h o se w all is lin ed w ith hig h ly v a c u o la te d c ilia te d e p ith e liu m and the o th e r h a lf, th e e p ith e liu m c o n ta in s v a r io u s ty p e s of gland c e lls . PLATE XVI 99 -C M ABGC- -C M -SDG SDG----- -FM C HDFG- -M C HDFG 54 -HDTG P L A T E XVII SECTIO N S O F C A EC U M AND P R O S T A T E GLAND F ig u re 55. S ectio n of th e c a e c u m . F ig u re 56. S ectio n of th e p r o s ta te gland show ing the h i s t o lo g ic a l s tr u c t u r e of the c ilia te d e p ith e liu m and the s u b - e p ith e lia l gland c e lls . PLATE XVII 101 MF ___ BS 0.17MM l NGC-------- % ‘ iè -------LU ____ CL # » # 0 .0 4 M M % # CE * N «t. CT L I T E R A T U R E C I T E D L IT E R A T U R E C ITED A bbott, R. T . 1954. A m e r ic a n s e a s h e lls . D . V an N o s tra n d C o m p an y , New Y o rk , pp. 2 78-279. A d a m s , H ., and A. A d a m s 1858. T h e g e n e r a of r e c e n t M o llu sc a . A d a m s G e n e ra of M o llu sc a , B o sto n , V ol. II, pp. 16-17; Vol. Ill, p la te s . A re y , L. B. 1916. T h e in flu en c e of lig h t and te m p e r a tu r e upon th e m ig ra tio n of th e r e tin a l p ig m e n t of P la n o r b is t r i v o l v i s . J o u r . C o m p . N e u ro l., 26(4): 3 59-389. C a r r i k e r , M. R . 1947. M o rp h o lo g y of the a lim e n ta r y s y s te m of the s n a il L y m n a e a s ta g n a lis a p p r e s s a Say. T r a n s . W isc o n . A ca. S c i., A r t and L e tt., 3 3 :1 -8 8 . C o le , E . C. 1941. C o m p a ra tiv e h isto lo g y . P h ila d e lp h ia : T he B la k is to n C o ., 395 pp. C o o k e, A. H. 1927. M o llu sc a and B ra n c h io p o d s . T he C a m b rid g e N a tu ra l H is to ry , 3: 4 2 9 -4 3 0 . E lio t, C. 1906. N u d ib ra n c h s and T e c tib r a n c h s fro m the In d o -P a c ific . J o u r . C o n ch ., L e e d s , 11(2): 3 1 0 -3 1 2 . F i s c h e r , P . H. 1883. M an u al de C o n c h y lio lo g ie . P a r i s : p. 559. F r e t t e r , V. 1939. T he s tr u c t u r e and fu n ctio n of th e a lim e n ta r y c a n a l of s o m e T e c tib ra n c h M o llu s c s, w ith a note on e x c re tio n . T r a n s . R oy. Soc. E d in b ., 59: 599-646. 103 104 G ilc h r is t, J . 1897. On the m in u te s tr u c t u r e of the n e rv o u s s y s te m of the M o llu sc a . J o u r . L inn. Soc. of London, 26: 179-186. G ould, A . A, 1855. E x p lo ra tio n s and s u rv e y s fro m th e M is s is s ip p i R iv e r to th e P a c if ic O c ea n , 5, A pp. A rt. Ill: 3 3 0 -3 3 6 . G ra y , J . E . 1847. A L is t of th e g e n e r a of r e c e n t M o llu sc a , t h e ir sy n o n y m a and ty p e s. P r o c . Z o o l. S oc., P a r t 15: 1 2 9 -2 1 9 . G u y e r, M. F . 1953. A n im a l M ic ro lo g y . T h e U ni. of C h ic ag o P r e s s , 308 pp. H offm ann, H. 1939. O p is th o b ra n c h ia . B ro n n . K l. O rd n . T i e r ., 3, A bt. 2, B uch 3, pp. 1 53-1222. I r e d a le , T . 1914. On som e in v a lid m o llu s c a n g e n e ric n a m e s . L ondon P r o c . M a la c . S o c., 11: 170-178. Jo h n so n , M. E ., and H. J . Snook 1935. S e a s h o re a n im a ls of th e P a c if ic C o a s t. T h e M a c m illa n C o m p an y , New Y o rk , pp. 4 1 1 -5 8 1 . K een , M ., and J . C . P e a r s o n 19 52. I llu s tr a te d k ey to w e s t N o rth A m e r ic a n g a s tro p o d g e n e ra . S tan fo rd : S ta n fo rd U niv. P r e s s , pp. 3 -3 6 . L e a c h , W . E . m G ra y , J . E . 1847. T h e c la s s if ic a tio n of th e B r itis h M o llu sc a . Ann. M ag. N at. H is to ry , 20: 2 67-273. L e o n a rd , R . E . 1918. E a r l y d e v e lo p m e n t of H am in e a . P u b . P u g e t Sound B io l. S tatio n , 2: 4 5 -6 3 . M a rc u s , E . 1956. N o tes on O p is th o b ra n c h ia . Sao P a u lo U niv., 7 : 3 5 - 3 7 . O ld ro y d , T . S. 1927. T h e m a r in e s h e lls of the w e s t c o a s t of N o rth A m e r ic a . S ta n fo rd U niv. P u b . S e r i., Vol. 2, p a r t 1, pp. 4 2 -4 4 . 105 P a r k e r , G. H. 1911. T he m e c h a n is m of lo co m o tio n in g a s tro p o d s . J o u r . M o rp h , and P h y s io l,, 22: 155-170. P e l s e n e e r , P . 1894. H e r m a p h ro d itis m in M o llu sc a , J o u r . M ic ro , S ci., 37: 19-46; pi, 4 -6 , P e r r i e r , R ,, and H. F i s c h e r 1911. R e c h e r c h e r a n a to m iq u e s e t h isto lo g iq u e s s a r la c a v ite p a lle a le et s e s d e p e n d e n c e s c h e z le s B u lle e n s . Ann. Sci. N at. Z o o l., 14:1-189. P r a t t , H. S. 1935, A m a n u a l of the c o m m o n in v e r te b r a te a n im a ls . P h i l a d elp h ia: T h e B la k is to n C o m p an y , pp. 573-575. S c h e e r, B , T . 1948. C o m p a ra tiv e p h y sio lo g y . New Y o rk : J o h n W iley and S ons, In c., pp. 159-232. S c h e p m a n , M. M. 1913. P u lm o n a ta and O p is th o b ra n c h ia T e c tib r a n c h ia ta . S iboga E x p e d . P a r t 49(1): 4 5 3 -4 7 6 , pi. 3 1 -3 2 . S m ith , M. 1945. E a s t c o a s t m a r in e s h e lls . E d w a rd s B r o th e r s In c., 150 pp. T h ie le , J . 1931. O p is th o b ra n c h ia . H andb. S y st. W e ic h tie rk u n d e , 1: 3 8 6 -3 8 7 . T r y on, J r . 1893. M an u al of C o nchology. P h ila d e lp h ia : C onchol. s e c t. A ca. N at. S c i., 15:351-376. T u rto n , W ., and J . F . K in g sto n in C a r r in g to n , N. T . 1830. T h e n a tu r a l h is to r y of the d i s t r i c t of T e ig n m o u th , D a w lish , and T o rq u a y . T he T e ig n m o u th , D a w lish , and T o rq u a y G uide, 230 pp. University of Lîbrsry

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Core Title Morphology and histology of the marine snail Haminoea vesicula

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