218 



THE ACEPHALA. 



<§. 199. 



ital organs are situated upon both sides of the body between the branchial 

 membrane and the muscular wall with which they are intimately blended. 

 They form, sometimes several round or angular projections divided into 

 two groups, and sometimes four long crests whose four distinct secretory 

 ducts open, after a short course, into the space included between the 

 branchial membrane and the muscular sac, at a variable distance from the 

 anal tube.^''* 



With the Brachiopoda, ovaries only have as yet been found. These 

 surround the liver, and stretch upon both valves of the mantle around the 

 minute branches of the branchial vessels.'''^ 



With the Lamellibranchia, there are both hermaphrodites and separate 

 sexes. But the last are much the more common ; for the first have as yet 

 been confined to Cydas,'^' Fecten,^^^ and Clavagella.'-^^ The testicles and 

 ovaries lie directly behind each other on each side of the body, between 

 the liver, intestine, and kidney. Their excretory ducts have not yet been 

 satisfactorily made out ; all that has been observed, is, that with Cyclas, the 

 eggs pass between the lamellae of the base of the external branchiae, and, 

 being here developed, produce sac-like swellings.'^"' 



With those species which are of separate sexes,*"^ the two ovaries or 

 testicles are situated usually in the sub-hepatic region of the abdomen. 



mentula). Tlie same arrangement has been ob- 

 served by Krohn (Froriep's neue. Not. No. 356, p. 

 49) with the testicle o{ P/iallusia, and by Philippi 

 with that of a Rhopalaea {Müller''s Arch. 1843, p. 

 48, Taf. IV. fig. 9). 



5 Cams has distinguished, with acuteness, from 

 the ovarian group, as being a testicle, a collection 

 of projecting angular glands lying with Cynthia 

 microcosmus, upon the internal surface of the 

 muscular sac (jileckeVs Arch. II. 1816, p. 577, 

 Tab. II. fig. 1, 2, &c. — and, Nov. Act. Acad. loc. 

 cit. Tab. XXXVII. fig. 1, 2, k. k.). Savigny 

 also (loc. cit. p. 92, PI. VI. fig. 2, 3) has seen with 

 Cynthia Tnicrocosmus, and pantex, two glandu- 

 lar groups with their excretory ducts as the sexual 

 organs, but without determining that one of these 

 was a testicle ; while Cuvier (loc. cit. p. 28, PI. I. 

 fig. 3. d. d.) who has observed the testicular 

 group with Cynthia microcosmus^ did not know 

 what to call it. According to Delle Chiaje (Me- 

 mor. &c. Tav. XLV. fig. 2, h. h.), the genital or- 

 gans of Phallusia phusa consist of numerous gland- 

 ular projections united into two groups, and hav- 

 ing two distinct excretory ducts. Witli Cynthia 

 canopus, the genital glands lie upon four long 

 crests, from the upper extremity of each of which 

 passes off an excretory duct towards the anal tube 

 (Savigny, Mem. loc. cit. p. 96, PI. VIII. fig. H, 

 2^). With Cynthia papillata, there are two of 

 these crests cui'ved in a loop-like mamier. (^Savig- 

 ny, loc. cit. p. 92, PI. VI. fig. 41, 4^, or Delle 

 Chiaje, Memor. III. p. 191, Tav. XLVI. fig. 1, 1. 1. 

 and Descriz;. &c. III. p. 27, Tav. LXXXII. fig. 11, 

 h. h.). From the two extremities of each of these 

 passes off an excretory duct ; and in comparing 

 this arrangement with that of Cynthia canopus, 

 it might be inferred that this loop-like disposition is 

 due to the fusion of two glandular crests. As to 

 which of these crests are ovaries and which testi- 

 cles, it would appear from Krohn (Froriep's neue 

 Not. No. 350, p. 50) that all are ovaries, for he has 

 observed, with a species perhaps identical with 

 Cynthia canopus, near the four oviducts, four other 

 excretory ducts not easily seen, and which, as l^asa 

 deferentia, arise from the ramified seminiferous 

 tubes spread out over the ovaries. 



6 For the ovaries of Terehratula and Orbicula, 

 «ee Owen, loc. cit. The figure of Müller (Zool. 



danica, I. p. 4, Tab. 5, fig 1, 7) of those of an Or- 

 bicula is very beautiful ; while that of Poli is not 

 as good (loc. cit. II. p. 191, Tab. XXX. fig. 19, 

 20). 



7 For the hermaphroditism of this genus see my 

 memoir in Mailer's Arch. 1837, p. 383. 



8 According to Milne Edwards (Ann. d. Sc. 

 Nat. XVIII. 1842, p. 322, PI. X. fig. 1), with 

 Pecten glaber, the male gland is situated at the ^ 

 upper, and the female gland at the lower part of 

 the abdomen. The two orifices found at the base 

 of the groove of the byssus belong to the testicles. 

 AVith another species of Pecten which I have ex- 

 amined, I was unable to confirm this hermaphro- 

 ditism, for I found in the abdomen only either 

 testicles or ovaries alone. Moreover the orifices- 

 just alluded to, appear to me to belong to a gland 

 secreting the byssus ; see above § 179, note 4. 



9 With Clavagella, Krohn found the testicles 

 beneath the liver, while the ovary surrounded it 

 and the stomach {Froriep's neue Not. No. 356, 

 p. 52). 



1Ü These pouches, which, with Cyclas, contain 

 but a single egg, have been figured by Carus (Erl- 

 äuterungstafeln, lift. III. p. 10, Taf. II. fig. 21). 3) 

 after Jacobson. 



11 Leeuwenhoek (Contiu. arcan. natur. detec. 

 Lugd. Batav. 1722, Epist. 95, p. 16) had already 

 distinguished male and female individuals with 

 certain Lamellibranchia. Notwithstanding this, 

 he afterwards affirmed that aU these Mollusks 

 were exclusively females, — an opinion still en- 

 tained by some naturalists (see Deshayes, in the 

 Cyclop. Anat. I. p. 700, and Garner, in the 

 Trans, of the Zool. Soc. II. p. 96). I had, however, 

 several years before, shown that the sexes were 

 separate with Unio, Anodonta, Mytilus, Ticho- 

 gonia, Cardium, Tellina, and Mya (Miil/er's 

 Arch. 1837, p. 380). The fact has been con- 

 firmed by Milne Edwards (Ann. d. Sc. Nat. 

 XIII. 1840, p. 375) with Fenus, by Owen 

 (Lectures, &c., p. 287) with Jnomia, and by Kal- 

 liker (Beiträge, loc. cit. p. 37) with Pholas. I can 

 also add to this list. Area, Pcctunculus, and 

 JLitliodomus. I have already mentioned (§196, 

 note 3) how Neuwyler, in taking the ciliary mo- 

 tions for those of spermatic particles, regarded the 

 kidneys of Anodonta and Unio as the testicles, 



