212 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



mantle cavity of the adult, and impregnation occurs internally instead 

 of externally, but it may also be said that the eggs and spermatozoa 

 come into contact in their passage out of the generative glands." It is 

 barely possible, indeed probable, if my memory serves me rightly, that 

 Davaine has put similar observations upon record. Horst also distinctly 

 asserts that the normal development of the embryos of Ostrea edulis 

 cannot take place outside of the parent. Mr. Berthelot, according to 

 Mr. Brandely, has discovered that the fluids in the mantle cavity of 0. 

 edulis contain albumen in a notable proportion, upon which the young 

 are supposed to be nourished. Mr. Brandely has found by direct experi- 

 ment, that in the case of 0. angulata it is possible to artificially impreg- 

 nate the eggs. His attempts to fertilize the eggs of 0. edulis with the 

 milt of 0. angulata and vice versa were unsuccessfully repeated at differ- 

 ent times for the last two years. I am now also uncertain in regard to 

 the identity of the species of which Lieutenant Winslow succeeded in 

 artificially impregnating the eggs at the mouth of the St. Mary's Biver, 

 in the Bay of Cadiz, Spain, which he says were natives, the variety 

 having existed and flourished in the bay for as far back as could be re- 

 membered. I quote his description of the specimens he used in his ex- 

 periments as follows: "In appearance they were quite similar to the 

 American species (Ostrea virginica), having long shells of from one to 

 three inches in length, rougher and thicker than is usually the case with 

 the European oyster." This remark raises the question whether the 

 experimenter was not really working with 0. aw#uZ«to instead of 0. edulis. 

 The locality where he got his specimens and where he conducted his ex- 

 periments also makes it not improbable that he was in reality working 

 the native unisexual species, 0. angulata. 



To return to the question of the breeding habits of Ostrea edulis, it 

 appears to me that we cannot very well question the authority of M6- 

 bius, Lacaze-Dutkiers, and Horst, in regard to the bisexual state of 

 the reproductive organs. My investigations also give some countenance 

 to the fact of a preponderance either of eggs or of spermatozoa in dif- 

 ferent individuals ; in fact, in some cases the one or other seems to be 

 almost exclusively the mature product. But we are not yet in a posi- 

 tion to arrive at a conclusion in this matter because of the scantiness 

 of the observations which have hitherto been made. The hypothesis- 

 that the spermatozoa are drawn from without into the generative ducts 

 by the ciliary action of the gills and mantle may be dismissed with the 

 remark that microscopic investigation, to my mind, has effectually dis- 

 posed of the probability of any such a state of affairs. We may see 

 the spermatozoa in course of development in the same follicle with the 

 ova, which is conclusive proof that the milt has not been derived from 

 without, from the water into which it had been discharged by neigh- 

 boring individuals. In truth, we find in some cases the spermatozoa pres- 

 ent so deep down in the utmost ramifications of the generative follicles- 

 that it is not conceivable that they should have been drawn in from 

 without. 



