35O CHARLES G. ROGERS AND KENNETH S. COLE. 



respect the run shown in Fig. 3 shows a marked variation from 

 the average. 



The average of seven runs is shown in Fig. 4, which gives the 

 approximate rate of heat production. The rate of heat produc- 

 tion per million unfertilized eggs is about 0.08 calories per hour, 

 while for the fertilized eggs after they have gone into the two 

 cells stage it is about 0.52 calories per hour. 1 Both of these 

 values are higher than those obtained by Shearer and by Myerhof 

 with other sea urchins, but the ratio of fertilized to unfertilized 

 eggs is the same. It should be pointed out that the results here 

 given must be taken as indicative rather than conclusive and 

 that further painstaking work is necessary. 



One feature of the curve shown in Fig. 4 deserves special 

 comment. It will be noted that the greatest rise in temperature, 

 i.e., the greatest period of heat production occurs immediately 

 upon fertilization. This certainly raises again the question as 

 to whether the process of membrane elevation depends upon an 

 oxidative process, set up by the sperm cell when it comes into 

 contact with the surface of the egg. 



It must be mentioned here that Loeb (3) had expressed in 

 1906 the view that the essential feature (or possibly one of the 

 essential features) of the process of fertilization is the increase 

 in the rate of oxidation in the egg, and that this increase is 

 caused by the membrane formation. Both Warburg and Loeb 

 and Wasteneys had shown that the rate of oxidation in the 

 sea-urchin egg is increased from 400 per cent, to 600 per cent, 

 upon the entrance of the spermatozoon and that membrane 

 formation alone, induced by artificial means, has the same result. 

 There is, therefore, a definite relation existing between membrane 

 formation and increased rate of oxidation. From Warburg's (8) 

 work it also seems likely that the increased oxidation occurs 

 chiefly at the surface of the egg. The fact that the greatest 

 heat production by the egg comes immediately after fertilization 

 seems to us to make it plausible to say that the entrance of the 

 spermatozoon induces a cortical' oxidation process, and that this 

 process results in the elevation of the fertilization membrane. 

 The almost explosive character of the heat evolution seems to 



1 This involves an energy liberation of approximately i erg per egg per hour. 



