(fossaria) (muiier) japan comparison

The malacological society of Japan

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The malacologicalsocietyof Japan

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Anatomy of Lymnaea (Fossaria) trancatula (MUIIer) from

Japan with the Comparison with the European Material

Hiroshi ITAGtxKi

Division of Veterinary Medicine, Faculty of Agriculture,

University of Tokyo, Tokyo

(muItt Pls. 2-5)

'

L,ymnaea (jFOssaria) truncatula (Mttller) is the common species in

Europe and other parts of the world, but it has not been known to

occur in Japan.. Recently, however, an introduced pond snail has

been found in our country, viz. Hokkaid6 and East Honsha (TOhoku

and Kant6 Districts) and it is obscure how and from where it has

been introduced into ouir country. This species is similar to L.

truncatula in shell feature. so I tried to clear up whether it was

that species or not in the anatomical aspect, too. L. truncatula is a

small species, so its detailed anatomy has not been undertaken ex-

c2pt sdch organs as the radula, the jaw and some parts of genitalia.

(Annandale 1925, Reichmuth 1936. Hubendick 1951. etc.)

I am indebted to Dr. Iwao Taki of the Hiroshima University

for read!ng the manuscript and invaluable advice, to Dr. Isao Taki

of the National Science Museum for his valuable suggestion and

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26 fi Xgft ee ftS 19 (1) ]956

encouragement and to Dr. W. S. S. van der Feen van Benthem Jutting

of Zo61ogisch Museum in Amsterdam for sending me the material

from the Netherlands. Thanks are also due to Professor Shin Okoshi

of the University of Tokyo for his active interest.

Material used was collected at Ajiki in Chiba Prefecture, where

the snails were generally found crawling on mud of rice fie!ds and

ditches or attaching itself to the substratum not in but above water

and laid egg masses on mud. The gelatinous, translucent egg mass

measures 4mm in length by 2.5mm or so in width and is soft,

containing about 15 eggs of O.60mm by O.58mm in both diameters

in average. In general the egg mass and the egg are smaller than

those of Ztymnaea (FOssaria> ollula and L. (Radix) j'mponica. '

' External anatomy

Shell thin and elongate ovate; colour light yellowish browii.

Whorls 5.5 in number, well rounded, smoeth except for many fine

growth lines. Suture we!1 indented. Aperture irot so much ex-

panded; columella generally not twisted; umbilicus narrow, fairly

deep. These shell features agree with those of European specimen

<Pl. 2, figs. 1, 2). ' .

The animal is of rather small size and has a small foot with a

fiat proboscis in front. Tentacles are triangular in shape. An eye

is situated at the inner base of the tentacle. In copulation the re-

versed penis is extended below the right tentacle. Body colour is

dark blackish grey in general, which is distinguishable.

Proportions among measurements of a shell are as follows ; the

percentage of width to height of shell varies from 48 to 54, that of the

larger diameter of the aperture･to the shell height 46 to 50, and that

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The malacologicalsociety of Japan

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of the smaller diameter of the aperture to width of the shell 59 to 66.

. Internal anatomy

The general position of visceral organs is shown in figure 4 of

plate 3. Most conspicuous organs are the right mid-gut gland (liver).

the stomach. the praeputium, and the mass-membrane gland.

Alimentary system: (Pl. 2, fig. 3; Pl. 5, figs. 8, 9, 10)

The small ovate muscular buccal mass (bm) is at the centre of

the proboscis (pb). A pair of salivary ducts empty at the･ supra-poste-

rlor surface of the buccal mass on both sides. which pass through the

nervous ring of the concentrated central ganglia. The form oi the

salivary gland (sg) is characteristic of the species and that of this

species shapes a lobular band in combining with each other both above

and beneath the initial part of the oesophagus (oe). The oesophagus

is a fairly long tube and a part of which is swollen.Iike the bird's

crop. The muscular stomach (st) is on the left side of the body a'nd

consists of the anterior and the posterior lumens. The intestine (in)

follows the posterior lumen. Compared with the large right mid-gut

gland (mgr) which occupies almost the entire spire except the body

whorl. the far smal!er left one (mgl) covers parts of the stomach and

of the looped intestine. These glands empty into the "duodenum"

on

the underside and a small caecum (ca) occurs shortly behind. whose

form is also of a specific character. The intestine grooves about on

the surface of the right mid-gut gland to become the rectum (rc)

which is a simple canal and opens near the anus at a short distance

behind the respiratory pore (ro) in the right mantle cavity.

The radula consists of an asymmetrical central tooth. having a

large cusp in the centre and a smaller one on each side and meas-



Themalacological society of Japan

28 fi l" t],: {e(k a,ki., 19 (1) 1956

uring about 61t in width, and about 24 lateral teeth on one sid3.

the first of which b2ing about 8.7pt in width.

Nervous system:(Pl. 3, fig.5; Pl. 4, fig. 6)

The central nervoug system is composed of concentrated ganglia

forming the oesophageal nervous ring, that is, a pair of cerebral (c),

pleural (pl, plr), and parietal (p, pr) ganglia and a visceral ganglion

(v). Besides these ganglia, a pair of pedal (pg) and buccal ganglia

(bg) exist. The former are situated beneath the cerebral and pleural

ganglia and connected with the cerebral and the pleural ganglia

by a thick connective respectively and the latter fasten themselves

to the posterior side of the buccal mass (bm) beneath the o2sophagus.

The anterior cerebral nerves are the nerves to the oral part, to

the proboscis, and to the tentacle. The oral nerve (the ventral pro-

boscis nerve) (bi) is thinner than the parietal proboscis nerve (bs).

The most conspicuous one (tn) goes to the tentacle, while the optical

nerve (on) is only a fine nervous thread of it. The same innervation

is also seen in other L,vmnaea species, The genital nerve

'to the

praeputium (pm) originates at the outer lobe of the right cerebral

ganglion (c) and runs on the undersurface of the praeputium. The

both pleural ganglia (pl, plr) are different in sizg. the right one

being ]arger, and the visible nerve does not start. The right

parietal ganglion (pr) is far bigger than the opposite one (p) and it

looks as if it were paired with the visceral ganglion (v). Two nerves

from each parietal ganglion are observed, one of whi'ch is thicker

than the other. The thicker left parietal nerve (pln) travels to the

left mantle and the thinner one (plp) does to the posterior body wall.

0n the other hand, the, inner nerve (prp) from the right parietal

'

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7RSK ac = i7 Jt" i) ese7 7i )ifi a.) nesu }th" EA Srt 29

g'anglion goes to the right body wall and the mantle, while the outer

thinner one (prn) does to the female genital opening to send a few

nervous threads. The visceral nerves occur at the posterior end of

the ganglion and one (vn) of them travels straight to the female

genitals and the digestive organs, while another (ngp) turns right-

wards to reach the female genital opening. Considering the nervous

distribution, the male genital organs are innervated by the right

cerebral ganglion and the female genitals are done by the visceral

one.

Both buccal ganglia are connected with each other by a very

short, thin commissure and supply the lateral part of tlie buccal mass

and the initial part of the oesophagus with fine nerves. A very

thin nerve is observed descending from the connective between both

buccal ganglia to the radula sac. The cerebro-buccal connective

occurs at the ventral side of the anterior part of the cerebral ganglion.

A comparatively small, oval pedal ganglion (p.cr) is under the

cerebral and the pleural ganglia and a triangular statocyst (sc)exists on the anterior part of that ganglion. These organs are spe-

cifically characteric in their forms. The pedal nerves. which have

not been examined by any other authors, are able to be roughly

separated into three parts: the anterior pedal nerves, the lateral

pedal ones, and the posterior pedal ones. A prominent nerve (pfa,

pfa') occurs on the antero-ventral side of the ganglion to innervate the

anterior part of the foot. Three nerves (nl. nl', pdr, pdr', etc.) are

found to supply the lateral part of the foot respectively and two

nerves travel posteriorly. One of them (pps, pps'), bei'ng fairly thin,

starts from the centre of the dorsal surface of the ganglion to the

'

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6fifi :




30 Rrc e･4J re itSi 19 (1) 1956

posterior dorsal part of the foot and the other conspicuous one (dpn,

dpn') enters deeply into the muscle to send nervous threads to 'L'he

posterior ventral part. .

Genital system:(Pl. 5, figs. 11, 12, 13) .

The hermaphrodite genital system consists of the hermaphrodite

part, the male genital one, and the female genital one.

The hermaphrodite part is composed of the hermaphrodite gland

(the ovotestis) (hg) and its duct (hd). The form of the hermaphro-

dite gland is of a specific character and that organ has a few large

projecting parts in this species. About the middle of the gland

occurs the hermaphrodite duct (hd), which is partially thickened.

The type of the thickening is also of an important specific character

being of symmetrically labular form in this species in general.

At the point, where the hermaphrodite duct empties into the duct

of the albumen gland (da). the male and the female genital part dif-

ferentiate. The male part consists of the prostate gland (prg), the vas

deferens (vd), the penis, the penis sheath (ps), and the praeputium

(pm). The prostate gland is elongate pyriform in shape and is a

reticulately pigmented organ followed by the vas deferens near its

distal end. The vas deferens (vd) enters into the muscle beside the

female genital pore and appears again near the base of the praeput-

ium. The male copulatory organs are also significant for specific

ldentification. The proportion of the penis sheath (ps) to the praep-

utium (pm) is about 1!3. Two long retractor muscles are attached

to the junction of the penis with the vas deferens and a long one

is at the initial part of the relatively simple praeputium. Moreover,

a few short ones are seen at the base of it.

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The female genital system is as follows: the fertilization chamber

(fch), the albumen gland (ag), the oviduct (od). and the egg-membrane

gland (mg) is most conspicuous of them all. A round fertilization

chamber borders upon the duct of the albumen gland, which is'a

comparatively prominent, whitish oval organ. The oviduct (od)

arises from the junction of the hermaphrodite duct (hd) with the

al'bumen duct (ad). followed by the uterus (ut). The white, cylindri-

cal egg-membrane gland is attached to the initial point of the uterus.

The mass-membrane gland follows the uterus and is white in colour,

having fine, darkly pigmented vessels on the surface. At some

distance from the female orifice. there opens the spermathecal duct

to the vagina. The spermatheca and the spermathecal duct are very

discriminative. In this species, the duct is very long compared with

the spermatheca, so L. (FOssaria) truncatula is able to be easily

distinguished from L. (Fbssaria) ollula by this character in spite of

the resemblance of their shells.

Circulatory system : (Pl. 4. fig. 7)

The blood vascular system of this species hardly differ from those

of other [,ymnaea species. having not b2en revealed. The heart is

situated before the transversally-running intestine on the left side

of the body, bordering the distal end of the kidney (kd). It consists

of one auricle (au) and one ventricle (vt). The great aorta (a) runs

over the intestine and ls divided into two smaller aortas. One of

them, the posterior aorta (pa), sends small arteries to the dorsal

surface of the stomach and reaches the posterior visceral organg,

while the other, the anterior aorta (aa), travels anteriorly after send-

ing a fine artery to the underside of the stomach. As soon as the

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32 .Ei,l ua fi7 sc i,k. 19 (1) 1956

anterior aorta passes through under the transversally-running inte-

stine, it gives a fine vessel to the oesophagus (goa) and then reaches

the mass-membrane gland to supply the female 'genital

organs. The

artery to the anterior organs, namely, the buccal mags, the praepu-

tium, etc., is separated from the mass-membrane gland and proceeds

anteriorly to pass through between the visceral and the right parietal

ganglion. The fine artery of the praeputium (ap) branches off from

it'

Respiratory system :

The respiratory chamber or the "lung"

is originally an enclosed

mantle cavity situated upon the transversally-running intestine be-

hind the kidney. The respiratory pore (ro) opens before the anus a

few millimeters away in the apex of the right mantle cavity and

the excretory duct opens in the pore.

Excretory system : (Pl. 3, fig. 4)

The ye!lowish lobular kidney (kd) is embedded in the mantle in

front of the "lung".

Its duct is not clearly distinguishable from

the glandular part and opens in the respiratory pore (ro), where

whitish excreted matter is seen to flow out.

Sense organ:(Pl. 4. fig. 6)

The statocyst (sc) is triangular in shape and situated in the

anterior part of each pedal ganglion (pg). The nerve to it is so fine

that it has not been defined.

Comparison with L. (Fbssaria) truncatula (MUIIer) from Europe

The specimens from Netherlands were collected at Midden-

Beemster (Province of North Holland) on 18th July. 1952. These

shells are a little smaller than JaPanese specimens : 7.lmm in max-




di[Cl: Ai Xg,ee =t ii pt" JZ, U S

imum length and 3.9mm

to eath other in the shell

The external appearance

The radula of Japanese material resembl

in the forms of the central

That is, the asymmetrical

central cusp is far greater

specimen (by Annandale)

in the marginal teeth.

different according to

Roszkowski (1927) in their

variation even ln a speclmen

on both sides of a row

member of the teeth,

fication of species in Lymnaeidae

studied had tricuspid lateral

nu!nerous cusps. The

teeth of the Japanese

one. while in the marginal

In the alimentary

ivary gland, littJe difference

Japanese materials.

surface of the "duodenum

Dutch specimen. The

observed in the genital

evident in the male system

penis, the penis-sac (the

=E 7 7V ff -t' 0[) geXllt}fiAS.lifIi ･X

33

in width and both specimens are similar

character.

is also identified in both specimens.

ed those of European specimen

and the first and the second lateral teeth.

central tooth has three cusps and the

than side ones, as the figures of a French

and a Swedish one (by Hubendick). But

the mode and the number of the cusp are

the authors. As stated by Baker (1911) and

accountg, the radular teeth show much

' and. moreover. in the same members

of teeth. This variation is found in every

so that the radula has no reliability for classi-

(Roszkowski 1927). The specimen

Leeth and elongated marginal teeth with

number and the form of cusps in the lateral

specimen were similar to those of the European

teeth they differed.

system, a specific character exists in the sal-

being found between the Dutch and the

Moreover, the caecum exserted on the under-

" was a little shorter than that of the

most important specific characters are usually

organs and Baker stated those were more

than in the female one; especially in the

praeputium) and the prostate. But according to





34

Ama e}e re itEi 19 (1) 1956

my

observation,

such genitalia as the spermatheca, the hermaphrodite

gland and its duct have also specific characters. The hermaphrodite

gland and

its duct or "vesicula

seminalis" of the Japanese specimens

were identified with those of the Dutch material, that is, the herma-

phrodite gland had not numerous small follicles but rather a few

Iarge

lobes, and symmetrical comparatively simple projections were

found in the duct of both specimens. No detailed account on these

genital parts of L. trancatula has been published. The spermatheca

has

its

long

duct, which is about tenfold of the sac-shaped part in length

and seems to have a permanent curvature just below the spermatheca

as

Reichmuth

figured. Furthermore. the male copulatory organs

have a few characteristics, namely, this species had few retractor

and protractor muscles. There were a lon.cr. muscle at the connective

part of the praeputium with the penis sheath and two long muscles at

the posterior part of the penis sac. It seems to be a specific character

that few

retractor

and the protractor muscles exist. Baker (1911) andRoszkowski

(1914) stated that the numb3r of these muscles had con- 'siderably

individual and local variations in L. auricularia, L. ovata.

L. stagnalis and L. Palustris. etc., but it appears to me that there

will be little variation in the attaching position of each set of mus-

cles.

Considering these points, the muscle of the male copulatory

organ may be of value to classify sp2cies. In fact, the results obt-

ained agreed

with those by Reichmuth (1936) and Hubendick (1951)in this point. Consequently the above mentioned differences seem tobe mere local variations and the Japanese specimen may be referable 'to lvmnaea (Fbssaria) truncatula (Mti11er).



The 　malaoologioal 　sooiety 　of 　Japan

丞垣・本邦産コシダカビメモノアラ．ガ．イの解剖学的研究 35

　　　　　　　　　　　　　　　　　　　　　　　　　　Summary

　　　　1． Adetailed 　anatomy 　 of 　 a 　fresh　water 　pond 　 snail 　recently

introduced 　 into　 Japan　 is　 descriもed ，　 compared 　 with 　 specimens 　 of

Lymnaea 　truncatula 　from 　theNetherlands 　by 　examining 　their　features．of 　both　shell 　and 　animal ．　 The 　species 　may 　be　referable 　to 　Lymnaea

（Fossaria）truncatula （MUIler）．

　　　2． Anatomic 母1　speci 丘c　characteristlcs 　were 　found 　in　such 　organs

as 　 the　 salivary 　gland ，　 the　 radula，　 the　 caecum

，　 the 　 hermaphrodite

gland ．　its　duct ，　the　pedal 　ganglion ，　the 　retractor 　muscles 　of 　the　male

copulatory 　organs 　and 　the 　statocyst，　 some 　 of 　 which 　have　 not 　been

attached 　 importance 　 as 　 speci 丘c　 characters ．

　　　3． Nervous 　 system 　 and 　blood　 vascular 　 system 　 are 　 similat 　 in

every 　 species 　 of 　 the 　 genus 　 Ly 〃 znaea，　 while 　 the 　 pedal 　 nerves 　 are

discriminative 　of 　species ．　 This 　fact 皿 ay 　be　assigned 　to　the　difference

in　the　ecological 　habit　of 　each 　species，　 especially 　 in　 its　 movement ．

　　　4． The 　egg 　mass 　and 　the 　egg 　are 　smaller 　than 　those 　of 　L ．　 o 〃ula

and 　L ・juPonica　fro皿　Japan　in　average ．　Eggs 　皿 easure 　O．60　by

O．58mm 　 in 　 average ．

　　　5・　L ・truncatula 　is　not 　so 　active 　in　motion 　and 　found 　us し【ally

on 　Inud 　above 　water 　in　rice 　fields　and 　ditches　in　Japan．

　1）近年わが国に移入されたコシダカモノアラガイについて解剖学的研究を行いその

精細を明かにした．．本種は殻によって Lymnaea 　truncatula （Mtiller）と同定されていた

が．軟体部の解剖の結果でも本種と同定される．

　2）本属は殻の類似するものが多く軟体部の特徴が分類に重要であるが，今までの歯

舌及び生殖器の外に唾腺，盲嚢（腸管），両性腺，足神経節，平衡器，雄性交接器に付着

する筋肉等の形態的特徴も亦重要である．

　3）　足神経系を除く神経系及び循環系には種的差異は余り見られない．足神経につい

ては従来余り記載されていないがその発達程度には可成りの差があり，これは陵息状況

N 工工一Eleotronio 　




36 fi twt ,tS tso 19 (1) 1956

}= I,kl Gk t}, 6 2: ,W, 2,)iL ts .

4) ijNgvgltoeijPtx L. ullula t1 -t1 7 i7 )i)'.t', L. japonica =E 1 77 ti

-r oits a) .#

}) ,tlN g < gff C･ ". HZ ifEl O.60 x O.58 mm -C･

k, 6 .

5) lkl tw (･tA.th, MIK :t= trU- ec,e.t6 t 2 (･Xt;･> < , e< zl< iZ! a) IEI .E fr mo -, -(

V ･6Dhi.;Il

E, 2L

:). ?il]lltiJei fii ip ?ESee-(Fe#itiLs.

References

1. Annandale, N. & H. S. Rao 1925: Materials for a re"ision of the recent

Indian Limnacidae. Rec. Ind. Mus. 27 (3): I37-189, 15 figs.

2. Baker, F. C. 1911: The Lymnaeidae of North and Middle America recent

and fossil. Chicago Acad. Sc. Spec. Pub. No. 3: 1-539, 63 pls.

3. Hubendick, B. 1951: Recent Lymnaeidae. Kungl.Svenska Vetenskapsakade-

miens Handlingar, Fji'rde Ser. 3 (1): 1-223, 5 pls.

4. Itagaki, S. & H. Itagaki 1955: Anatomical and ecologica! studies on Lymmea

oZlula, as the snail intermediate host of the liver fluke, including the rela-

tion to the prevalence of fascioliasis. Sci. Rep. Azabu Veterinary Coll. No.

2: 1-16, 3 pls.

5. 0koshi, S. & H. Itagaki 1955 : Comparative anatomy of three common pond-

snails from Japan; Lymnaea ollula, L. 1'ciponica, and L. truncatuta. Jap. J.

Parasitol. 4 (2): 27. (In Japanese).

6. Reichmuth, W. 1936: Dje Leberegelschnecke Galba truncatula MtM.: zugltich

Ein Beitrag zur Systematik der SUsswasser-schneckenfamilie Lymnaeidae.

Z. Morpho!. Okol. Tiere, 31 (2): 207-244.

7.' Roszkowski, W. 1914: Contribution a 1'6tude de I'anatomie de 1'appareil

g6nital chez Limn6es du sous-genre Guqnaria Leach. Extra. Compt. Rend.

Suc. Sci. Varsowie. 7, 1-12, 11 figs.

8. '-L'" l927: Contribution to the study of the fami!y Lymnaeidae. VII.

The genus Pseudostfccinea.from South Brazil. Ann. Zool. Mus. Polonici, Hist.

Nat. 6: 1-33, 17 figs.

9. Taki, Is. 1939: Mollusca of Jehol: Lymnaeidae. Rep. Ist. Sci. Exped. to

Manchoukuo. V-1-1-4: 160-183, 8 pls.

Reference letters

a=aorta ag=albumen gland

aaL-anterior aorta ap=artery of praeputium

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IS(tE: 1<5ifi,ee = ti of± lt s =e 7 7 s j'l a) geewdr".thii":ee

au=auricle

bg=buceal ganglion

bi =ventral nerve of proboscis

bm::=buccal mass

bs=parietal nerve of proboscis

c=:cerebral ganglion

ca == caecum

cpc =cerebro-pedal connective

da=duct of albumen gland

dpn=-right deep posterior pedal

nerve

dpn'=L'ieft deep posterier pedal

nerve

e =T- eye

eg'--egg-membrane gland

fch--fertilization chamber

gn=genital nerve

goa=gastro-oesophageal artery

hd=hermaphrodite duct

hg==hermaphrodite gland

hia=hepato-intestinal artery

in=intestine

kd=kidney

mdl=duct of left mid-gut gland

mdr=duct of right mid-gut gland

mg=mass-membrane gland

mgl='left mid-gut gland (liver)mgr=-:-right mid-gut gland (Iiver)ngp=nerve to female genital pore

nl=right lateral pedal nerve

nlr:=Ieft lateral pedal nerve

od=ovjduct

oe=oesophagus

on=:optic nerve

p=left parietal ganglien

pa--posterlor aorta .

pb=proboscis

37

pdr--right postere-!atera! pedal nerve

pdr･'=left postero-Iateral pedal nerve

pfa==-right anterior pcdal nerve

pfa'==left anterior pedal nerve

pg==pedal ganglion

pl=left pleural ganglion

pln=!eft anterior parietal nerve

plp=:Ieft posterior parietal nerve

ptr=:right pleural ganglion 'pm=praeputlum

ppc ==pleura-pedal cennective

pps=:right superficial posterior pedal

nerve

pps'==left superficial posterior pedal

nerve

pr==right parietal ganglion

prg=prostate gland

prn=anterior right parietal nerve

prp==-posterior right parietal nerve

ps==penis sheath

r=retractor rnuscles of rnale copura-

tory organ

rc=rectum

ro=respiratory orifice

sc :- statocyst -

sg==salivary gland

sp==spermatheca

spd=-=-spermathecal duct

st==stomach

t=tentacle

tn==tentacular nerve

ut･ L-uterus

v=visceral ganglion

vdL-vas deferens

vg==vaglna

vn=visceral nerve '

vt=ventricle




3S

Plate

1.

2.

'3.

Plate

4.

5.

Plate

6.

7.

Plate

8.

9.

10.

11.

12.

13.

' Rma i>. re tig 19 (1) 1956

Explanation of Plates 2-5

2

lvmnaea truncatula (MUII.) from Japan. Length: 7.9mm, width: 4.0mm..

Specimen from the Netherlands, 7.0mm in length and 39mm in width

(the largest specimen obtained).

Radula. C: central tooth. Number shows Iateral and marginal teeth.

3 '

Visceral .organs in dorsal view. Some of them removed from the rnatural

position.

General topography to show nervous system except pedal nerves in dorsat 'vlew.

4 .

Pdda! nervdus system.

Circulatory system. Some organs are taken away. Dorsal view.

5

Sa!ivary g!and, combining each other to form a ring.

Ventral view of "duodenum'L

showing a caecum and ducts of both

mid-gut glands.

Alimentary system in dorsat view.

Male copulatory organ and its retractor muscles.

The part where the mate and the female genital organs different-iate.

The fertilization chamber opens to the duct of the albumen gland.

Genital system in dorsal view.

.





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