^214. 



THE CEPHALOPHORA. 



243 



fices are usually situated opposite each other; but in some they are so 

 approximated that the stomach has the form of a caecum.*''* 



The intestine, having made more or less numerous ® convolutions, seldom 

 forms a rectum, but opens, usually, close by the respiratory orifice on 

 the right side of the anterior end of the body, and rarely at the posterior 

 extremity/"* With the Pectinibranchia, the rectum often projects widely 

 into the cavity of the mantle, as a longer or shorter prolongation upon 

 whose extremity the anus is situated. 



Sagitta and the Apneusta present wide difi'erences from this just- 

 described type of structure. With the first, the mouth opens into a short 

 oesophagus which passes directly, without any stomachal dilatation, into 

 the intestine ; this last runs straight backwards, and, curving downwards, 

 terminates in the anus situated on the median line of the ventral surface 

 at the posterior end of the body.'^"* With the Apneusta, on the other 

 hand, there is a stomach with several and often highly-ramified caecal 

 appendages — which, in some species, extend even into the dorsal append- 

 ages. A short rectum follows directly upon the stomach, and ends in 

 an anus, often difiicult to be found, and situated at the anterior part of the 

 right side of the body.'*^' 



cartilaginous lamellae, and the third has, beside, 

 numerous horny hooks which point forwards 

 (Cuvier, loc. cit. PI. III.). 



7 Miirex, Foluto, Sigarelus, Phyllidia, Di- 

 phyllidia, and many species of Doris and Cari- 

 naria. 



8 The intestine is very short and slightly tortu- 

 ous with Clio, Carinaria, Thetis, Triionia, 

 Diphyllidia, Pleurobranchaea, Buccinum, Mu- 

 rex, and Janthina. With the other Cephalo- 

 phora, it has usually many convolutions, which are 

 quite numerous especially with Haliotis, Patella, 

 and Chiton (Cuvier, loc. cit. PI. I.-III., and Poll, 

 loc. cit. Tab. III. fig. 6). 



y With the Pectinibranchia, and most of the 

 Pulmonata, whose anus is near the respiratory 

 orifice, the position of the first is determined by 

 that of the last, and therefore is most usually upon 

 the right, and rarely upon the left side. This is 

 tlie case also with nearly all the other Gastero- 

 poda. 



With Patella, it is situated directly back of the 

 head ; with Tritonia, Scyllaea, and Thetis, a 

 little further back ; and even still more behind 

 with Diphyllidia, Dolabella, Notarchus, and 

 Pleurobranchaea. In this last genus it is above 

 the branchia, while in Pleurobranchiis, and Aply- 

 sia, it is behind this organ. With Chiton, Phylli- 

 dia, Doridium, Bullaea, Te.itacella, and Onchi- 

 dirnn, it is at the very posterior end of the body. 

 With Doris, and Polycera, it is somewhat elevated 

 on the side of the back and surrounded by bran- 

 chiae. 



With Haliotis, it is anterior and on the left side ; 

 and with Sigarctus, Fissurella, and Emarginula, 

 it is even in front of the oral cavity. 



Its position is varied with the Ileteropoda and 

 Pteropoda. With Carinaria, and Pterotrachea, 

 it is situated at the base of the intestinal sac, — 

 with Atlanta, upon a prolongation of the right side 

 of the neck ; with Phyllirrhoe, upon the middle of 

 the right side ; with Pneumodermon, directly 

 behind the right pinion ; with Tiedemannia, at 

 the middle of the abdomen ; with Hyalaea, at the 

 same point but a little at the left ; and v/ith Cym- 

 bulia and Limacina, in tiie respiratory cavity. 

 See, for these various positions, the works esiwc- 

 ally of Cuvier, Meckel, and ( an lieneden. 



10 Krohn, loc. cit. p. 8. 



11 Fur the intestinal canal of the Apneusta, see 

 Milne Edwards, Ann. d. Sc. Nat. XVIII. 1842,'p. 



330, PI. X. fig. 2 (Calliopaea), also Quatrefages. 

 Alder, Hancock and Embleton, Alhnan, and 

 Nordrtiann, loc. cit. According to a communication 

 from Kblliker, that of Rhodope is the most simple ; 

 it consists only of a caecum which extends even to 

 the posterior extremity of the body, and near the 

 cardia sends off a short caecum which passes along 

 the left side of the oesophagus to the pharynx, and 

 upon the right side of the other end of the body 

 terminates in a short rectum. With Actaeon, ac- 

 cording to Souleyet (Compt. rend. XX. 1845, p. 94), 

 the intestine, after forming a stomachal dilatation, 

 bends, first forwards, then backwards, opening on 

 the right side of the neck. But the descriptions and 

 figures of this animal by Quatrefages (Ann. d. Sc. 

 Nat. I. p. 141, PI. IV. flg!^, V. "iig. 4) and Allman 

 (loc. cit. p. 148, PI. VI.), are remarkably contradict- 

 ory to these statements of Souleyet. According to 

 these authors, the stomach is followed by a short 

 rectum opening upon the right side of the neck, 

 which is attended by two superior and two in- 

 ferior intestinal tubes which send numerous ram- 

 ified appendages into the parenchyma of the body. 

 With Chalidis, the oesophagus is followed by four 

 caeca, the two shortest of which extend in front, 

 and the others behind. With Peita, there is a 

 large intestinal tube having many short coecal ap- 

 pendages, situated in the middle of the liody. With 

 Aeolis, Flabellina, Tergipes, which have only a 

 single intestinal tube closed posteriorly, ;ind with 

 Zephyrina, Anrphorina, and Calliopaea, which 

 have two such, the caeca from this canal extend 

 even into the dorsal appendages. With Eolidina, 

 which has three intestinal tubes intercommunicate 

 ing by numerous transversal anastomoses, these 

 last give rise to the caeca of the dorsal append- 

 ages. Quatrefages (Ann. d. Sc. Nat. XIX. p. 285, 

 PI. XI. fig. 2, c), who at first declared that the 

 median tube of tljese animals opened by an anus 

 at the posterior end of the body, has since (Compt 

 rend. XIX. p. 811) i-ectified this error ; for here, 

 as also with Actaeon, Aeolis, Tergipes, and Rho- 

 dope, the anus is anterior and on the right side. 



A similar correction will jjerhapa be made with 

 Vcnilia, whose stomach, according to Alder and 

 Hancock (Ann. of Nat. liist. XIII. p. 163, PI. II. 

 fig. 7), not only sends many ramified caeca in^o 

 the lateral appendages of the body, but also is fol- 

 lowed by a rectum, opening, tliey s:iy, at the pos- 

 terior portion of the back. 



