<^220. 



THE CEPIIALOPHORA. 



249 



tion is cutaneous, which, with the Apneusta, is probably favored by 

 ciliated epithelium,*^' With some of these species, there is an aquiferous 

 system which also serves, perhaps, for respiration.*"^ 



/. Branchiae. 



§ 220. 



With nearly all the Cephalophora, excepting the Pulmonata, there is a 

 Branchial apparatus ; this is usually very contractile, and always covered 

 with very lively cilia. '^' It is composed either of lamellae, or of filaments 

 arranged in rows or in bundles, or of plumose or pectinate ramified prolon- 

 gations. With some, the branchiae are situated, uncovered, on the back or 

 on the sides of the body ; with others, they are more or less covered by the 

 mantle ; but with the majority, they are contained in a special cavity of 

 this last. 



This Branchial cavity communicates externally by the Siphon, which is 

 simply a canaliculated, contractile prolongation of the mantle itself.'-' 



1. With the Pteropoda, the respiratory organs are very unequally devel- 

 oped. In some genera, they appear wholly wanting, while in others, there 

 is a spacious branchial cavity containing one or two groups of fringed 

 lamellae from which pass out as many veins towards the auricle of the 

 heart. '^* 



2. With most of the Heteropoda, there is, upon the median line of the 

 posterior part of the back, a pectinate or plumose branchial apparatus, 

 which connects with the heart by a short vein.**' 



3. This apparatus is most variable as to form and situation with the 

 Gasteropoda, and the diiferent groups of this class are founded upon its 

 modifications. The Cirribranchia have a bundle of small filaments on 

 each side of the neck.*'^' The Nudibranchia have on each side of the back, 

 in one or more rows, or in a circle upon the middle of the posterior part 



2 The opinion that the dorsal and lateral append- 

 ages of Aeolis, JDolidina, Fenilia, Zephyrina, 

 Amphorina, Flabellina, Calliopaea, and Ter- 

 gipes, are branchiae, is untenable, since it has 

 been shown that they contain i^rolongatious of the 

 digestive canal. 



3 For the aquiferous system of Actaeon, and 

 Venilia, see below, § 222. 



1 For the ciliated organs of the branchiae of 

 Gasteropoda, see Sharpey, Cyclop. Anat. &c. I. 

 p. 619. 



2 For the branchial apparatus of the Cephalo- 

 phora, I must refer principally to the works of 

 Cuvier (Memoires, &c.), Savi^ny (Descript. de 

 I'Egypte, loc. cit. II. PI. I.-III.), Meckel (Bei- 

 trftge zur vergleich. Anat., and Syst. d. vergleich. 

 Anat., loc. cit.), Quoy and Gaimard (Voyage de 

 I'Astrolabe, or Isis, loc. cit.), and Delle Chiaje 

 (Mem. and Descriz. loc. cit.). 



3 With Clio, one does not know what to think of 

 the form and position of their respiratory organs, 

 since that Eschricht (loc. cit. p. 5, 16) has shown 

 that the vascular net-works observed by Cuvier 

 upon the two fins of these animals (Mem. loc. cit. 

 p. 5), and which have been taken for branchial 

 vessels, are only muscular fibres. Fan Beneden 

 also, could find no respiratory organs with Lima- 

 cina and Cuvieria. Moreover, more accurate ob- 

 servations are required to determine whether or not 

 the four-rayed cutaneous appendage of the poste- 



rior extremity of Pneumodermon, and the circu- 

 lar cutaneous lobe in the same locality with Spon- 

 ^iobranchaea, are really branchiae ; see Cuvier, 

 Mem. loc. cit. p. 7, PI. B. fig 1-6, g. ; Fan Bene- 

 den, loc. cit. p. 49, PI. I. fig. 1, d. {Pneumoder- 

 mon) ; and D'Orbis^ny, Isis, 18S9, p. 497, Taf. I. 

 fig. IX. 1-3, 11, 12 {Spongiobrancliaea). On the 

 other hand, Van Beneden (loc. cit. p. 17, 40, PI. 

 I. fig. 2, 12, III. 1, 5, 6) has distinctly seen bran- 

 chiae and branchial veins in Hyalea, Cymbulia and 

 Cleodora. In the first of these genera, tliere lie 

 in a very large respiratory cavity situated on the 

 back of the intestinal sac, numerous brancrhial lam- 

 ellae arranged in an arcuate manner, and bound 

 together by a branchial vein. In the other two 

 genera, the cavity of the mantle has, on each side, 

 a fan-shaped branchia. See also Delle Chiaje, 

 Descriz. &c. I. p. 89, Tav. XXXIV. fig. 9, 11. 



4 With Atlanta, the single branchia is simple, 

 pectinated, and always concealed in the interior of 

 their cell (Rang, loc. cit. p. 378, PI. IX. fig. 12, 

 or Isis, loc. cit. p. 473, Taf. VII. fig. 12). With 

 Carinaria, and P-terotrackea, the branchia is also 

 simple, but very developed and dcmi pinnate, and 

 in the first of these genera it projects outside the 

 shell {Delle Chiaje, Mem. loc. cit. Tav. XIV. 

 XV. LXIX., and Descriz. loc. cit. Tav. L.XIII.-IV.). 



5 Dentalium, according to Deshayes, loc. cit. 

 p. 334, PI. XV. fig. 12, or Isis, loc. cit. p. 464. 

 Taf. VI. fig. 16. 



