630 OYSTERS, AND ALL ABOUT THEM. 



We admit that the ova of salmonidcz, from their size, 

 are much more readily submitted to artificial fertilization 

 than those of the angulata, but however large a figure may 

 be given to the losses attendant upon the application of 

 the same methods to the ova of bisexual oysters, their 

 artificial fecundation would none the less prove a productive 

 operation. Let us see what occurs in a state of nature. 

 The female oyster emits ova in considerable numbers ; but 

 how few of them meet in the immense extent of water that 

 which will instil into them the principle of life ? To 

 estimate this is difficult ; but if we assume the proportions 

 indicated above, we find that out of 20 millions of ova 

 which may be emitted by the parent, 2 millions only arrive 

 at the state of moving larvce. 



Having reached this phase of transformation, how 

 many will become attached to the collectors ? One must 

 not expect that the tenth of what survives will escape the 

 multiplied dangers with which it is constantly surrounded. 

 In closed waters it is otherwise. In the first place, impreg- 

 nation is guaranteed to all ova capable of being fertilised by 

 placing them in forced contact with the fecundating 

 element. Thus is suppressed the first cause of loss, which 

 is doubtless the most important. We escape a second 

 cause, which is also serious, in keeping the embryos 

 in closed reservoirs, where, sheltered from all the various 

 dangers to which they would be exposed in the open, they 

 pass tranquilly the period of their erratic existence till the 

 arrival of the time when they feel the necessity of attach- 

 ing themselves to the collectors which they find within 

 their reach. 



Figures will be more eloquent than the best of argu- 

 ments. 100 ova fertilised have produced 80 moving larvce. 

 This is the average, according to our experience, which 



