OYSTER CULTURE IN FRANCE. 615 



Such is the course adopted when it is sought to dis- 

 cover whether individuals belonging to kindred species, or 

 to varieties of the same species, are capable of contributing 

 to the formation of a new individual. Frequently, when 

 the subjects are kindred species, or varieties of the same 

 species, although the cross in fecundation may not result 

 in the production of any living animal, or any likely to live, 

 the elements are brought together, and fecundation takes 

 place several times. Sometimes even the ovum is formed, 

 and attains a greater or less degree of development, &c., 

 but when the same elements brought together remain un- 

 altered, an absolute sterility may be concluded. 



This is precisely what we have had to observe in the 

 attempts at direct hybridation which \ve have made during 

 two years, last year and this year. 



At different times, and in different media, we have 

 brought into contact the ova of Portuguese oysters and the 

 fecundating liquor of the ordinary oyster, and vice versa, 

 and in no case in the conditions in which our experiments 

 have been conducted have the elements shown any natural 

 approach to each other ; in no case has there been any 

 trace of fecundation or development. 



EXPERIMENTS IN ARTIFICIAL FECUNDATION. 



When, two years ago, we had arrived at certainty in 

 the separation of the sexes in the ostrea angulata, we per- 

 ceived at once the possibility of the fecundation of this 

 mollusc by artificial methods. We were, moreover, encou- 

 raged by the experiments of M. Brooks, of the University 

 of Baltimore, which he had made on the Virginia oysters, 

 which are equally unisex, experiments which had allowed 

 him to follow the development of the embryo as far as to 

 the formation of the shell. 



