322 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



blended properly and fecundation took place; sometimes also the ovule 

 would segment and attain a more or less advanced degree of develop- 

 ment, etc.; but when these same elements were brought into immediate 

 contact they remained unchanged, and ended in absolute sterility. 



This is precisely what we have observed in theconrseof direct attempts 

 at hybridization which we have made during the past two years — last 

 year and this. 



At different times and under different conditions we have brought the 

 eggs of the Portuguese oyster and the milt of the common oyster into 

 contact, and vice versa; never under these experimental conditions, the 

 sexual elements not being brought into contact naturally, has there 

 been a trace of evidence of successful fertilization or of development. 



ATTEMPTS AT ARTIFICIAL IMPREGNATION. 



When after two years we had learned for a certainty that the sexes 

 of Ostrea angulata were confined to separate individuals, we immediately 

 conceived that it was possible to artificially fertilize the eggs of this 

 mollusk. We were likewise encouraged by the experiments which 

 Brooks, of the Johns Hopkins University of Baltimore, had made upon 

 Ostrea virginica, likewise unisexual, and which had enabled him to 

 follow the development of the embryos to the formation of the shell. 



We began some experiments in the laboratory of embryogeny of the 

 College of France, which, without being conclusive, indicated none the 

 less the path to be pursued, and the manner in which onr experiments 

 were to be conducted. In the course of the same year these experi- 

 ments were repeated at Arcachon without much success. Last year we 

 obtained mobile larvae for the first time. The observation much sur- 

 prised us; we had not long to wait, for after an incubation of only 

 twelve hours, a precocious outward manifestation of life was apparent, 

 for already in this phase of their evolution these larvae presented an 

 appearance which left no doubt as to their definitive form. 



On the other hand, we have found nothing in what iias been pub- 

 lished on the subject of the incubation and transformation of the eggs 

 of Ostrea edulis which recalls the aforementioned phenomenon of pre- 

 cocious movement which had not, we believe, been observed before.* 

 The advanced state of the season where we were, and the difficulties 

 which we had to procure Portuguese oysters at Arcachon in a condi- 

 tion fitted for spawning purposes, did not permit us to continue the 



*At the time when they occupied themselves busily with tin- artificial fecundation 

 of tish ova, tin* two Vosgian fishermen, Gehin and Remy, Bonghl to discover, or had 

 stated that it would be possible to trout the eggs of the common oyster, the only na- 

 tive species known at that time, by the same methods. Bnt the hermaphroditism of 

 the mollusk having been demonstrated, the] were obliged to abandon this hope. 

 Moreover, had the artificial fecundation been possible, it would have been of no con- 

 sequence industrially, for the reason that tin- eggs ami embryos of Ostrea edulis cannot 

 develop ontside of the incubatory cavit\ of the parent. 



