OYSTER AND MUSSEL REPORT. 105 



was certainly very warm. When run from the seawater 

 taps in the Zoological Station I found it was at 74°F. with 

 a specific gravity of 1/023, out in the middle of the 

 "bassin" I found it at 76°F. with a specific gravity of 

 1*024, while over the shallow oyster pares I found it 

 varying from 78°F. to 80°F. with a specific gravity of 1 '022 

 to 1024, and in one or two corners of the pares at low 

 tide where the last of the ebb had been exposed to the 

 midday sun it rose as high as nearly 90°F. 



The cultivators at Arcachon are of opinion that the 

 oysters could not be bred successfully, that there would 

 not be a sufficient deposit of spat, in waters that are much 

 cooler, but we have evidence to the contrary in what Captain 

 Dannevig says in regard to the plentiful spawning of the 

 oyster in his pond at Norway, and also in the deposits of 

 spat on the North Coast of France and South Coast of 

 England. The temperature in July in Dannevig's pond at 

 Arendal was about 63°F. ; while at Port Erin, Isle of Man, 

 the temperature in the bay during the first week in July 

 varied from 59° to 62- F., and on July 22nd was 59°F. 

 with a specific gravity of 1*025, -and shore pools near the 

 Biological Station, fairly comparable with the oyster pares 

 at Arcachon, ranged in temperature on July 22nd from 

 59°F. to 76°F., and on July 13th from 60° to 76°F. 



I am very hopeful that although the specially high tem- 

 perature of the ''bassin" at Arcachon — and possibly still 

 more the calm weather during the critical period when the 

 young animal is free-swimming and then settling down 

 for life — may have favoured an unusually heavy deposit 

 of spat, still no such great heat is really necessary for a 

 normal amount of reproduction and development, and that 

 we may have in our neighbourhood water sufficiently 

 warm for the purpose. 



As to the specific gravity : —it varies at Arcachon from 



