OYSTER CULTURE IN FRANCE. 623 



and this is diluted on a slip of glass by employing a quantity 

 of water equal to several times the volume of the portion 

 of matter. 



In the case of a female the liquid becomes granulous, 

 and upon examining it carefully, ova may be distinguished 

 which have been detached by the water. In the case of a 

 male the mixture of the seminal fluid and the water is 

 effected with greater difficulty, and the liquid remains 

 opaque and milky. 



With the aid of a magnifying glass this investigation 

 is made extremely easy. 



The choice of the reproductive specimens is not, there 

 is reason to believe, immaterial to the success of the oper- 

 ation. Care must be taken not to use oysters procured 

 from raised positions, which are frequently left high and 

 dry. * 



We have never with them obtained good results. The 

 fecundation may take place, the separation proceeds some- 

 times to a considerable degree, but all at once the develop- 

 ment stops, the eggs change, and their membrane bursts. 



To avoid all disappointment of this kind, it is desir- 

 able to proceed with subjects taken from lively and deep 

 waters. It is also always important to be satisfied that the 

 elements to be employed have arrived at their maturity. 



* Our opinion as respects the sterility of certain specimens rests 

 upon two important observations made in the Isle of Oleron. We 

 have tried in vain to fertilise oysters taken from the raised portions of 

 the oyster concessions of the island, while at the same moment, with 

 the same conditions, in the same medium, with the same water, and 

 under the same external influences, the experiments have resulted in 

 the formation of moving larvae, if the specimens employed were taken 

 on the same part of the coast, but from the deeper portions. Never- 

 theless, we claim for ourselves reservation upon this point. 



