§ 220. THE CEPHALOPHORA. 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.” 
I. 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 
eae 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. 
each side of the neck. 
The Cirribranchia have a bundle of small filaments on 
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 deolis, Holidina, Venilia, Zephyrina, 
rior extremity of Pneumodermon, and the circu- 
lar lobe in the same locality with Spon- 
Amphorina, Flabellina, Calliopaea, and Ter- 
gipes, are branchiae, is untenable, since it has 
‘been shown that they contain prolongations of the 
‘digestive canal. 
8 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. 
619. 
2 For the branchial apparatus of the Cephalo~ 
phora, I must refer principally to the works of 
Cuvier (Mémoires, &c.), Savigny (Descript. de 
PEgypte, loc. cit. II. Pl. I.-III.), Meckel (Bei- 
trage zur vergleich. Anat., and Syst. d. vergleich. 
Anat., loc. cit.), Quoy and Gaimard (Voyage de 
PAstrolabe, or Isis, loc. cit.), and Delle Chiaje 
(Mem. and Descriz. loc. cit.). 
8 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 (Mém. Joc. cit. 
p. 6), and which have been taken for branchial 
vessels, are only muscular fibres. Van 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- 
gtobranchaea, are really branchiae ; see Cuvier, 
Mém. loc. cit. p. 7, Pl. B. fig 1-6, g.; Van Bene- 
den, loc. cit. p. 49, Pl. I. fig. 1, d. (Pneumoder- 
mon) ; and D’Orbigny, Isis, 1839, p. 497, Taf. I. 
fig. IX. 1-3, 11, 12 (Spongiobranchaea). On the 
other hand, Van Beneden (loc. cit. p. 17, 40, Pl. 
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, there lie 
in a very large respiratory cavity situated on the 
back of the intestinal sac, numerous branchial 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, Pl. IX. fig. 12, 
or Isis, loc. cit. p. 473, Taf. VII. fig. 12). With 
Carinaria, and Pterotrachea, the branchia is also 
simple, but very developed and demi pinnate, and 
in the first of these genera it projects outside the 
shell (Delle Chiaje, Mem. loc. cit. Tav. XIV. 
XY. LXTX., and Descriz. loc. cit. Tav. LXDL-IV.). 
5 Dentalium, according to Deshayes, loc. cit. 
p. 334, Pl. XV. fig. 12, or Isis, loc. cit. p. 464. 
Taf. VI. fig. 16. 
