352 CHARLES G. ROGERS AND KENNETH S. COLE. 



sea water. The curve approaches 10 micro-volts as an asymp- 

 tote, but reaches 50 per cent, of that value in about 90 minutes. 

 From this it will be seen that if there is an excess of sperm it 

 may seriously affect results during the first twenty or thirty 

 minutes. 



As has been pointed out this method can not be used over 

 long periods of time with the desired degree of accuracy. It 

 also has the disadvantage of requiring large numbers of eggs, so 

 that the longer they run, the more they tend to fall out of step, 

 and so tend to mask any effect that may be present. This 

 latter difficulty will remain, of course until it is possible to work 

 with a single egg. The apparatus is being redesigned so that it 

 will be possible to follow the heat production of both eggs and 

 sperm under varying conditions over longer periods of time. It 

 is planned to extend the work so as to include other forms. 



SUMMARY. 



The heat production of the eggs of A rbacia punctnlata has been 

 measured before, during, and following fertilization, through 

 development into the eight cell stage. It has been found that 

 the rate of heat production at the instant of fertilization is ten 

 to twelve times that of the unfertilized egg. After fertilization 

 the rate of heat production decreases constantly for twenty 

 minutes, when it reaches about 65 per cent, of the value at 

 fertilization, and remains constant until the first cleavage, at 

 about 50 minutes after fertilization. At the first cleavage the 

 rate drops suddenly by more than 10 per cent., and then remains 

 constant until the eggs are in the eight cell stage, which is as far 

 as the work has been carried. The rate of heat production of 

 the unfertilized eggs was found to be about 0.08 calories per 

 hour per million eggs, and that of the fertilized eggs about 0.52 

 calories per hour per million eggs after the one cell stage. 



An experiment on Arbacia sperm indicates that when placed 

 in contact with sea water, its heat production is similar to that 

 of an exothermic chemical reaction of the first order. 



The suggestion is offered that the heat evolution occurring 

 immediately upon fertilization is the result of an oxidative 

 process which takes place in the cortex (chiefly) of the egg and 

 which leads to the elevation of the fertilization membrane. 



