340 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



lot, contains albumen in a notable proportion. It was in vain that we 

 attempted to preserve the embryos of 0. edulis in renewed and aerated 

 sea- water until their complete development, even though they had at- 

 tained the state of white or that of gray fry. The white embryos died 

 after two or three days, the gray embryos after twelve or fifteen days, 

 although they were in the presence of collectors to which they could 

 attach themselves. 



These facts show the essential differences between the two species of 

 oysters, and exclude all idea of interbreeding and make us reject the 

 preconceived theory of hybridization entertained by some ostracul- 

 turists. We have, moreover, made direct experiments in hybridization 

 which gave only negative results. In this manner, in several attempts 

 last season and this, we have brought together the eggs of the Portuguese 

 oyster and the zoosperms of the common oyster, and reciprocally; 

 never, under the conditions where we have experimented, the sexual 

 elements not being brought together naturally and instinctively, was 

 there a sign of fecundation or of development. 



The sexual elements of 0. angulata being, as one might say of them, 

 clearly separated, we have conceived the possibility of achieving their 

 artificial fecundation. The example of Brooks, of the [Johns Hopkins] 

 University of Baltimore, who had made successful attempts in the arti- 

 ficial fecundation of Ostrea virginiana, was, to say the least, encourag- 

 ing. 



Here is, after numerous experiments, the mode of fecundation which 

 we have adopted. It is easy, after some experience, to distinguish the 

 sexes of the adults with the naked eye. We detached the eggs from 

 the ovary by means of a camel's hair pencil, and they were then placed 

 in a vessel filled with sea-water — a vial, for example. To separate them 

 and free them from the foreign matters with which they are surrounded, 

 we shook the vial for a few moments, when the liquid was allowed to 

 stand. The eggs which are fit for fecundation then fall to the bottom 

 of the vessel ; that which remains in suspension is to be thrown away. 

 Decanting the latter we renew the water in the vessel, and it is suffi- 

 cient to add a small portion of seminal liquor, upon which the eggs are 

 immediately surrounded and rolled by the mobile zoosperms; the first 

 phases of fecundation commence soon afterward. 



The ova and spermatozoa retain their vital properties for several 

 hours, without being in contact, in water. Our most successful experi- 

 ments were made with elements which were not brought into contact 

 until two or three hours after their extraction from the genital glands. 



We will not describe the first phases of development of the eggs, but 

 we think there deserves to be mentioned a fact which has not hitherto 

 been observed, viz, that the embryos of 0. angulata commence to swim, 

 according to temperature, at from seven to twelve hours after fecunda- 

 tion. At Verdon we have had them to do so in seven hours, the water 

 having a temperature of 22° [0. 71° F.j Their movements of translation 



