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.'''' 



AVith 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 Cyclas,'-''' Pecten,'-*^^ 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. 



mcntula). The same arrangement has been ob- 

 served by Krohn (Froriep\^ neue. Not. No. 356, \>. 

 49) with the testicle of PhaUusia, and by Philippi 

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

 48, Taf. IV. fig. 9). 



5 Cams has distinguished, with aouteness, from 

 the ovarian group, as being a testicle, a collection 

 of projecting angular glands lying with Cyntliia 

 microcosmus, upon the internal surface of the 

 muscular sac {MeckeCs Arch. II. 1816, p. 577, 

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

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

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

 Cynthia microcosmus, and pantex, two glandu- 

 lar groups with their excretory ducts as the sexual 

 organs, l)ut without determinuig 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 Dette Chiaje (>Ie- 

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

 gans of Phaltusia pluisa consist of numerous gland- 

 ular projections united into two groups, and hav- 

 ing two distinct excretory ducts. With Cyntliia 

 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 papitlata, there are two of 

 these crests curved in a loop-like manner. (Savig- 

 ny, loc. cit. p. 92, PI. VI. fig. 4', 4^, or Dette 

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

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

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

 p ..lies off an excretory duct ; and in comparing 

 this arrangement with that of Cyntliia 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. 356, 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 P'asa 

 deferentia, arise from the ramified seminiferous 

 tubes spread out over the ovaries. 



(! I'lir the ovaries of Terebratula and Orbicula, 

 see Owen, loc. ciL. The figure of Mutter (Zool. 



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

 bicuta is very beautiful ; while that of Poti is not 

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

 20). 



7 For the hermaphroditism of this genus see my 

 memoir iu Mutter's Arch. 1837, p. 383. 



8 According to Mitne Edwards (Ann. d. So. 

 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. 

 With another species of Pecten which I have ex- 

 amined, I was unal)le 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. 



y With Ctavagella, Krohn found the testicles 

 beneath the liver, while the ovary surrounded it 

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

 p. 52). 



l'> Tliese pouches, which, with Cyclas, contain 

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

 auterungstafeln, lift. III. p. 10, Taf. II. fig. 2l>. 3) 

 after Jacobson. 



n Leeuwenhoek (Contin. 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 all 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, Tettina, and Mya {Milller's 

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

 firmed bv Mitne Edwards (Ann. d. Sc. Nat. 

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

 (L'-'Ctures, &c., p. 287) with Anomia, and by Kiit- 

 liker (Beitrage, loc. cit. p. 37) with Photas. I cau 

 also add to this list, Area, Pectunculus, and 

 Lithodomus. 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 aud Unto as the testicles, 



