INTRODUCTION 13 



compressed in the ovary, they can be caused to form membranes 

 and to cytolyze. Moreover, starfish eggs that are caused to 

 develop by shaking form membranes first of all; this is the 

 immediate effect of the mechanical agitation. 



8. We may now raise the question as to how the artificial 

 membrane formation induces the development of the egg. The 

 writer reached the conclusion that for the sea-urchin egg this 

 was due .to an acceleration of oxidations. This suggestion was 

 confirmed by Warburg, and since by Wasteneys and the writer. 

 The entrance of the spermatozoon raises the rate of oxidations in 

 the egg of the sea-urchin to from four to six times its usual 

 amount; and the artificial membrane formation has the same 

 effect. There are two possibilities by which this result can be 

 produced: either a catalyzer (an oxidase) is carried into the 

 egg by the spermatozoon; or the change in the surface layer 

 itself causes the increased rate of oxidation. Everything 

 speaks in favor of the second assumption. We know that with 

 the concentration of the catalyzer the rate of chemical reactions 

 increases either in proportion to the concentration of the cata- 

 lyzer or in the ratio of the square root of the concentration; 

 and the investigations of the temperature coefficient of develop- 

 ment of the egg show that the rate of development is deter- 

 mined by chemical reactions. If therefore the spermatozoon 

 increased the rate of oxidation by carrying an oxidase into the 

 egg the rate of segmentation in an egg fertilized by more than 

 one spermatozoon should be increased in the ratio of 1:2 or 

 1 : i/2. Observations show that the velocity of segmentation 

 in eggs fertilized by two spermatozoa is identical with that 

 found in eggs fertilized by one spermatozoon. This fact proves 

 that the spermatozoon causes development, not by carrying an 

 oxidase or some other catalyzer into the egg, but by removing 

 an obstacle to development. The same must hold for the 

 explanation of the influence of membrane formation upon 

 development. Through the cytolysis of the cortical layer 



