252 



TUE CEPIIALOPIIORA. 



S^ 223. 



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

 filled with water, from which nullifying 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 lalors. 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 Accphala and 

 Cephalophora. 



CHAPTER VIII 



ORGANS OF SECRETION. 



/. Urinary Organs. 



§ 223. 



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

 even, lamellate gland, which is usu<xlly situated near the branchial or princi- 



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

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

 erous system, arising from a reservoir of water 

 situated beliind the heart, and wliich he lias called 

 Pochc pu/monaire, wliich is spread thr.aigh 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. tig. 4, a. a. b.) has also 

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

 blood system. The canal, which, with Venilin, 

 ojiens at the posterior part of the back, and which 

 has been taken by 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 figured liy De/le Cliiaje 

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

 the same region, wtih Aeolis cristata {FetiiUa .'). 



^ Delle. Chiaje is as yet the only naturalist who 

 has published (juite detailed researches upon the 

 aquiferous canals of the Cephalophora indicated in 

 the text. In an earlit-r work, he has described 

 them with Dnris, I'/ictis, Aplijsia, Pleuro- 

 branchus, r/eiirijljronr/i(ira, liii//a, Doridinm, 

 Diphtjllidia, Tiirbo^ Trnclius, Nerita, Conns, 

 Ci/praea, yoluta, liiiccinum, Murex, Ceri- 

 thium, Rostellaria, halioti.i, and Patella, as 

 canals which traverse the foot, opening, for the 

 most part, on its biir<lers Ijy nu'ierous orifices (see 

 his Descrizione di un nuovo a])i)arato di caiiali ac- 

 <;uosi scoperto negli auimali iiivertelirati marini, 

 in his Memor. &•;. II. p. 'iSJ, Tav. XVII. fig. 10- 

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

 w.iich, he says, is wanting with the aqu;ilic I'ulmo- 

 ii.L^.i, as a beautiful, subcutaueous 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, 

 Hyatea, Caiinaria, Pterotracliea, Doris, Tri- 

 tnnia, Thetis, Pleurobranchaen, Diphyllidia, 

 Doridium, Gasteropteron, Aplysia, ISiiUa, Si- 

 garetus, and Javthina). 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 Cliiaje, Descriz. loc. cit. Tav. 

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



'■i Meckel (Syst. d. vergleich. Anat. VI. p. 72) 

 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 (luantities 

 of water, without the need of special orifices. 

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

 or Froriep'.i neue Not. No. 733, p. 9S) 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 e.xosmose. Van Beneden, also (Ann. d. 

 Se. 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 othiM- hand, he is inclined to admit that, with 

 Aplysia, and Carinaria, kc, there are small ori- 

 fices by means of which these animals can mix 

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

 and I'lnstitut. No. 627, or Froriep's neue Not. flo 

 727, p. 4, and No. 797, p. C5). 



