OYSTER CULTURE IN FRANCE. 629 



But this is particularly to be noticed, that there would 

 be not merely one harvest each year, but two, and perhaps 

 three harvests. In fact, as the season for spat lasts at least 

 for three months, this period of time is sufficient, as we 

 have conclusively proved at Verdon, to allow of collectors 

 being placed three times in the same claire, and being 

 withdrawn as often covered with spat. 



There is no want of spots fitted for the reception of 

 establishments for hatching. 



Such spots would be found at the mouth of the majority 

 of our rivers. Only two conditions are necessary; brackish 

 water weighing according to the areometer from ^\ to 3 

 degrees, and facility for the introduction of fresh water into 

 the reservoirs. We may, perhaps, better display the advan- 

 tage and economy of our system in borrowing an example 

 from river pisciculture. 



It is known with what success the ova of fish are dealt 

 with under the methods of artificial fecundation, the laws 

 of which M. Coste has determined and fixed. The scourge 

 of the depopulating of waters having, so to speak, spared 

 no European State, the question of pisciculture is, to some 

 extent, the order of the day everywhere, and it ranks with 

 those questions of economy which demand a prompt 

 solution. Hence the special laboratories of pisciculture 

 which have been created in Switzerland, Germany, England, 

 Russia, Norway, &c. Artificial fecundation is their grand 

 point, and forms the base of their operations. This is 

 because it gives results far superior to those which would 

 be obtained if nature were left to act freely. Thus out of 

 1,000 ova treated artificially, and kept in incubating vessels, 

 980 are hatched perfectly; while in natural waters the losses 

 are reckoned at 90 out of the 100. 



