BACTERIOLOGY OF THE OYSTER. 83 



food and oxygen remains sufficient and the lower the temperature 

 the longer this period will be. The oyster does not close on account 

 of "rigor frigoris," for the control of the adductor muscle is still very 

 marked at a temperature of l.l'^C., and is scarcely distinguishable 

 from normal. 



Mitchell/ in an extended study of the oxygen requirements of 

 shellfish states as one of his conclusions that "oysters of medium 

 sizes, at temperatures between 19° and 28°C., used from 7 to 35 deci- 

 milligrams of oxygen per hour per 100 grams of entire weight. The 

 amount varies with the temperature, so far as experiments show, 

 according to simple relationship, so that the curve approximates 

 a straight line." . . . "The common clam (Mya Arenaria) 

 shows a higher oxygen requirement than the oyster." 



The theory of hibernation which the writer has advanced appears 

 to be in harmony with the experiments of Mitchell on the oxygen 

 requirements of oysters. The lower the temperature the less the 

 amount of oxygen used. But no matter what the temperature so 

 long as the oyster is living it needs a certain amount of oxygen to 

 carry on its oxidative processes. When the amount available within 

 its shell is exhausted, it will open to renew its supply. 



The statements of practical oyster growers also leads to the same 

 conclusion. It is said that oysters from Narragansett Bay in February 

 cannot be shipped very far in the shell, because, as the oyster men say, 

 they will "cluck," that is, open their shells and allow the shell liquor 

 to run out. The explanation no doubt is that during the "zero 

 weather" of January, the oysters are closed and as their oxygen 

 requirements under the circumstances are small they can remain 

 closed for sometime without exhausting the supply available in the 

 shell liquor. The period of cold weather, however, is sufficiently long 

 perhaps to allow the oysters, even with their small requirements, to 

 nearly, if not quite exhaust the available supply of oxygen within 

 their closed shells. The result is that in February when they are 

 removed to the opening house or express car which has relatively a 

 much higher temperature than the water from which they were taken, 

 the metabolic processes of the oyster are greatly increased and 

 there is a demand for more oxygen. The supply within the shell, 

 which has already been greatly reduced, is quickly used up, and 

 consequently the oyster opens to renew its supply. 



iThe Oxygen Requirements of Shellfish, Bull. U. S. Bureau of Fisheries, XXXII, 1912, 209. 



