252 



THE CEPHALOPHORA. 



§ 223. 



for, upon the back and directly behind the heart, there is a reservoir 

 filled with ^Yater, from which ramifying canals pass off in all directions/^' 

 The older observations upon these aquiferous canals of the Pteropoda, 

 Heteropoda, and Gasteropoda, have been but indifferently increased by 

 more recent labors. With these Cephalophora, the substance of the 

 envelope of the body is permeated by a beautiful net-work of wall-less 

 canals, which are filled with water, it is supposed, through several orifices 

 upon the surface of the body.*-' It is, nevertheless, far from being settled 

 that these canals belong to an aquiferous system, for the existence of their 

 external orifices is doubtful, and it may be urged that they are only a con- 

 tinuation of the venous system.*'' At all events, this question demands 

 further researches based upon facts observed with the Acephala and 

 Cephalophora. 



CHAPTER VIII 



ORGANS OF SECRETION. 



/. Urinary Organs. 



§ 



99' 



With most of the Cephalophora, the Urinary apparatus consists of an un- 

 even, lamellate gland, which is usually situated near the branchial or princi- 



1 According to Soiileyet (Compt. Rend. XIX. p. 

 360, XX. p. 93), there is, with Actaeon, an aquif- 

 erous system, arising from a reservoir of water 

 situated beliind tlie heart, and wliich he has called 

 Poc/ie pulmonaire, which is spread through the 

 whole of the body. Vogt, as he has written me, 

 has distinctly seen this system with a canal open- 

 ing on the right side behind the anus. Allman 

 (loc. cit. p. 148, PI. V. fig. 4, a. a. b.) has also 

 observed it in the same species, but he took it for a 

 blood system. The canal, which, with Venilia, 

 opens at the posterior part of the back, and which 

 has been taken bj» Alder and Hancock (loc. cit. 

 XIII. PI. II. fig. 1, 7, b.) for the rectum with its 

 anus, belongs also, perhaps, to an aquiferous sys- 

 tem, as well as the orifice fieured by Delle Chiaje 

 (Descriz. loc. cit. Tav. LXXXVIII. fig. 2, d.) in 

 the same region, wtih Aeolis cristata {Venilia 1). 



2 Delle Chiaje. is as yet the only naturalist who 

 has published quite detailed researches upon the 

 aquiferous canals of the Cephalophora indicated in 

 the text. In an earlier work, he has described 

 them with Doris, Thetis, Aplysia, Pleuro- 

 branchus, Pleuroliranc/iaea, Bulla, Doridium, 

 Diphyllidia, Turbo, Trochus, Nerita, Conus, 

 Cypraea, Folut.a, Buccinum, Murex, Ceri- 

 thiuni, Rostetlaria, Haliotis, and Patella, as 

 canals which traverse the foot, opening, for the 

 most part, on its borders by numerous orifices (see 

 bis Descrizione di uu nuovo apparato di canali ac- 

 (juosi scoperto negli animali invertebrati mariiii, 

 in his Memor. &c. II. p. 259, Tav. XVII. fig. 10- 

 15). Since then, he has described this system, 

 «'l:icii, he says, is wanting with the aquatic Pulmo- 

 iiaci., as a beautiful, subcutaneous net-work. lie 



has named it Apparato idro-pneumatico or Sis- 

 tema linfatico-venoso ; see his Descriz. I. p. 88, 

 &c., Tav'. XXXII. XXXIV. XL. &c. (Cymbulia, 

 Hyalea, Carinaria, Pterotrachea, Doris, Tri- 

 tonia, Thetis, Pleurobranchaea, Diphyllidia, 

 Doridium, Gasteropteron, Aplysia, Bulla, Si- 

 garetus, and Janttiina). With Cymbulia, and 

 Gasteropteron, this aquiferous canal communi- 

 cates with a large sinus from which passes off a 

 long afferent canal which projects from the surface 

 of the body (see Delle Chiaje, Descriz. loc. cit. Tav. 

 XXXII. tig. 1, 2, g. LV. fig. 2, b. f. 4. c. a.). 



3 Meckel (Syst. d. vergleich. Anat. VI. p. 12) 

 positively denies the existence of an aquiferous 

 system and its external orifices. But he maintains 

 that the marine Cephalophora can absorb and re- 

 ject simply by their skin, considerable quantities 

 of water, without the need of special orifices. 

 Milne Edwards (Compt. Rend. XX. p. 271, 

 or Froriep's neue Not. No. 733, p. 98) declares 

 that this apparatus, such as described by Delle 

 Chiaje, belongs to the venous system. He also 

 denies the existence of external orifices, explain- 

 ing the ingress and egress of water which has 

 been observed with these animals, as due to endos- 

 mose and exosmose. f^an Beneden, also (Ann. d. 

 Sc. Nat. IV. 1835, p. 250), says that he is convinced 

 that with Aplysia the so-called aquiferous canals 

 are only a dependence of the venous system. On 

 the other hand, he is inclined to admit that, with 

 Aplysia, and Carinaria, &c., there are small ori- 

 fices by means of which these animals can mix 

 water with their blood (Compt. Rend. XX. p. 520, 

 and I'Institut. No. 627, or Froriep^s neue Not. No 

 727, p. 4, and No. 797, p. 65). 



