^ 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 Pulnionata, 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 different 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- rior extremity of Pneumodermon, and the circu- 

 ages of Aeolis, Eolidina, Fenilia, Zephyrina, lar cutaneous lobe in the same locality with Spon- 

 Amphorina, Flabellina, Calliopaea, and Ter- ^iobranchaea, are really branchiae ; see Cuvier, 

 ffipes, are branchiae, is untenable, since it has Mem. loc. cit. p. 7, PI. B. fig 1-6, g. ; f^an Bene- 

 been shown tliat they contain prolongations of the den, loc. cit. p. 49, PI. I. fig. 1, d. {Piieumoder- 

 digestive canal. mon) ; and D''Orbi^ny, Isis, 1839, p. 497, Taf. I. 



3 For the aquiferous system of Actaeon, and fig. IX. 1-3, 11, 12 (Spong-iobranchaea). On the 

 Venilia, see below, § 222. other hand. Van Beneden (loc. cit. p. 17, 40, PI. 



1 For the ciliated organs of the branchiae of I. fig. 2, 12, III. 1, 5, 6) has distinctly seen bran- 

 <Jasteropoda, see SAarpe^, Cyclop. Anat. &c. I. chiae and branchial veins in i/j/a/ea, CyTTiftH/iVi and 

 p. 619. Cleodora. In the first of these genera, there lie 



2 For the branchial apparatus of the Cephalo- in a very large respiratory cavity situated on the 

 phora, I must refer principally to the works of back of the intestinal sac, numerous branchial 1am- 

 Cuvier (Memoires, &c.), Savigny (Descript. de ellae arranged in an arcuate manner, and bound 

 TEgypte, loc. cit. II. PI. I.-III.), Meckel (Bei- together by a branchial vein. In the other two 

 träge zur vergleich. Anat., and Syst. d. vergleich, genera, the cavity of the mantle has, on each side, 

 Anat., loc. cit.), Quoy and Qaimard (Voyage de a fan-shaped branchia. See also Delle Ckiaje, 

 PAstrolabe, or Isis, loc. cit.), and Delle Chiaje Descriz. &c. I. p. 89, Tav. XXXIV. fig. 9, 11. 

 (Mem. and Descriz. loc. cit.). 4 With Atlanta, the siugle branchia is simple, 



3 With Clio, one does not know what to think of pectinated, and always concealed in the inferior of 

 the form and position of their resph-atory organs, their cell {Rang, loc. cit. p. 378, PI. IX. £g. 12, 

 since that Eschricht (loc. cit. p. 5, 16) has shown or Isis, loc. cit. p. 473, Taf. VII. fig. 12). With 

 that the vascular net-works observed by Cuvier Carinaria, and Pterotrachea, the branchia is also 

 upon the two fins of these animals (Mem. loc. cit. simple, but very developed and demi pinnate, and 

 p. Ö), and which have been taken for branchial in the first of these genera it projects outside the 

 vessels, are only muscular fibres. Van Beneden shell {Delle Chiaje, Mem. loc. cit. Tav. XIV. 

 also, could find no respiratory organs with Lima- XV. LXIX., and Descriz. loc. cit. Tav. LXIJ I. -IV.). 

 cina &nä. Cuvieria. Moreover, more accurate ob- 5 Z)en<a/iM7n, according to Deshayes, loc. cit. 

 eervations are required to determine whether or not p. 334, PI. XV. fig. 12, or Isis, loc. cit. p. 464. 

 tlie four-rayed cutaneous appendage of the poste- Taf. VI. fig. 16. 



