16 



acini, on the inner walls of wliich the ova or eggs and 

 spermatozoa are developed. The eggs in the female 

 gTOw from ovicells, and in the male the spermatozoa 

 originate from cells which are known as spermogens. 



In having a pair of openings, one on either side for the 

 escape of the generative products, our oyster agrees per- 

 fectly with that of Europe, according to H. Lacaze-Du- 

 thiers." Davaine,-!- in his memoir, asserts both in his 

 text and in his figures that the generative glands of the 

 European oyster have three oj^enings on either side, 

 statements which are not in accord either with facts or 

 analogy. In a paper by Sir Everard Home, which we 

 have noticed before, he erroneously regards the supra- 

 branchial or upper gill cavity as an oviduct. 



ISTo evidence to show that our oyster is hermaphrodite 

 was found during the entire season, nor were my searches 

 for embryos or eggs on the mantle and in the gills any 

 more successful than those carried on two years before 

 by Prof. Brooks. There is no doubt whatever that the 

 oyster of Europe nurses its young on its mantle and gills 

 for some time, nor can we very well question the very 

 high authority of Mobius for saying that in most cases 

 the sexes are separate, and that but one kind of pro- 

 ducts, viz. : either eggs or speimatozoa are at any one 

 time found in the generative organs; Lacaze-Duthiers' 

 observations seem to confirm the conclusions of Mobius. 



As the eggs and spermatozoa ripen and are set set free 

 in the little terminal sacs or acini of the generative or- 

 gans, they are probably pushed or driven out of the larger 

 canals which connect with the terminal sacs, and which 

 join the main oviduct oi\ by means of cilia which line 

 these canals, as suggested by Lacaze-Duthiers, just as 

 the food is carried to the mouth and the water continu- 

 ally forced through the gills by the waving of the innu- 



*Recherches sur les Organes genitaux des Acephales Lamellibfanches. Ann des Sci. Natu 

 relies. 4 ser , zool., t. 2, pi. 8, pp. 214 — 228. Paris, 1855. 



fMem. de la Soc. de Biol. IV, 1852, pp. 297 — 339, pis. I — II. 



