WATER ENTERINO THE BLOOD. Ill 



excited sufficient notice. Consider it, for a moment, and 

 you will remark that water entering the general cavity must 

 mingle with the blood, and that largely. But if it mingles 

 thus freely Avith the blood, on its entrance, will it not also 

 on its exit carry away a portion of the blood ? It will, and 

 does, as any one may prove experimentally. Agassiz has 

 described it in detail, apropos of the Mactra* and suggests 

 that the pores of the fish may have a similar office. In the 

 ActinicB and Acalephce the free passage of water to and 

 fro is well known. In several Annelids {Eunice, Nereis, 

 &c.), I have little doubt that the openings which exist on 

 each side of the body, between every two feet, and which 

 permit the passage of the ova into the surrounding water, 

 are aquiferous tubes, through which the water passes to and 

 fro. These openings were first described by Eathkd ; and 

 Siebold admits that through them the water may probably 

 pass. M. Quatrefages, however, a great authority on the 

 subject of Annelids, is disposed to deny the existence of 

 these openings : " J'ai vu chez I'Eunice sanguine des ap- 

 parences rappelant un jieu 1 'observation de Eathke ; mais 

 ces orifices, s'ils existent, ont ^videmment pour objet de servir 

 a la sortie des oeufs ; c'est la du moins ce que I'analogie 

 permet d'admettre. Je n'ai jamais vu pondre ou ^jaculer 

 une Annelide errante."-!- What ]\I. Quatrefages has not been 

 fortunate enough to have seen, has several times been 

 witnessed by me. I have seen the eggs issuing from these 

 openings, the existence of which he is inclined to dispute ; 



* Siebold u. K6i,UK^B.—Zeitschrift.f. Wissen. Zoolog. vii. 176. 

 t Quatrefages in Annales des Sciences XaL, 1850 ; xiv, 298. 



