230 WILLIAM RAY ALLEN. 



('09), Krogh ('14) and others have shown that the rate of meta- 

 bolic processes is related to body temperature. In this case the 

 decrease in temperature probably directly affects the rate of secre- 

 tion of the typhlosole glands. It is not improbable that a seasonal 

 metabolic rhythm exists. 5 



In order to test the effect of temperature alone in this matter 

 and to eliminate the other possible elements, the following experi- 

 ment was carried out : 



Checks were kept at room temperature. In each repetition of 

 the experiment one jar was placed in the cold water of the outlet 

 of an artesian well. When the temperature was sufficiently re- 

 duced the experimental starved animals were introduced into 

 their respective jars. Meantime concentrations of lake plankton 

 were made by filtering through fine bolting-silk, and the plankton 

 remaining in the bucket washed out into the check and experi- 

 mental jars. Each mussel had a jar to itself. The water in all 

 had a decided green tint when agitated, for the concentration was 

 in all cases from 100 volumes to i. The jars were well shaded 

 to eliminate the possible action of sunlight in orienting the plank- 

 tonts, and thus keeping the food equally available to all. The 

 amount of water was equalized, and the mussels so placed that the 

 exhalent stream played obliquely upon the sides of the jar and 

 maintained an eddy to keep the planktonts in circulation. 



The material was collected at about 10:00 A.M.. and about 

 three hours were allowed for the temperature adjustment. The 

 experiments began at about i :oo P.M., and continued from three 

 to four and one-half hours, usually four. The average tempera- 

 ture of the experimental jars at the beginning of the experiments 

 was 13.4 C, varying between 12.6 C. and 14.0 C. The aver- 

 age of the same jars at the end of the experiments was 13.1 C., 

 varying between 12.0 C. and 14.4 C. There was an average 

 loss in temperature of 0.3 in these jars. The checks gave an 

 average at the beginning of 26.0 C., varying between 23.6 C. 

 and 30.0 ; at the end an average of 27.2 C., and a variation 

 between 24.0 and 29.6 C. The average rise in temperature of 



5 The crystalline style of Mya arenaria is reformed more rapidly during 

 summer than winter. Edmondson (I. c.) ascribes this to the increased metab- 

 olism of the approaching breeding season. 



