FERTILIZATION REACTION IN ECHINARACHNIUS PARMA. 9 



through study of fertilization in the most diverse types of ova and 

 by rejection of the incidental phenomena for the basic and com- 

 mon. What is the common factor in fertilization? So far as we 

 know, it is some type of cortical change. But by cortical change 

 we do not mean that the sign of the thing is the thing itself. 

 Thus membrane separation in the sea-urchin egg is an easily visible 

 sign of cortical change. Membrane separation, however, is not 

 fertilization.' It is here that an error lies in much of the work on 

 experimental parthenogenesis. 



Though we may doubtless gain knowledge of the nature of the 

 cortical changes following insemination through study of these 

 changes experimentally induced, we can not rely wholly on such 

 work to explain fertilization. A far more simple mode of attack 

 is to study fertilization itself. And if, in addition, the theory of 

 the action of the agent in experimental parthenogenesis is erro- 

 neous, such a theory for fertilization can but hinder the solution 

 of our problem. If it be true that cell division is not fertilization, 

 it is equally true that experimental parthenogenesis is not fertiliza- 

 tion. We must, therefore, study the fertilization process itself, 

 the common factor of which is some kind of cortical change. 



The evidence at hand indicates that the cortical changes in fer- 

 tilization are due to an instantaneous, irreversible reaction between 

 an ovogenous substance, fertilizin, and the spermatozoon. Stated 

 in these terms the theory almost demands that the cortex is neces- 

 sary for fertilization. The evidence herewith submitted points to 

 this conclusion. The primary, if not, indeed, the whole event in 

 fertilization, is the cortical reaction. The succeeding events with 

 concomitant physical and chemical changes leading to cell divi- 

 sion and development are the consequence of a complete cortical 

 reaction between fertilizin and spermatozoon. 



LITERATURE. 

 Chambers, Robert, Jr. 



'21 Studies on the Organization of the Starfish Egg. Jour. Gen. Phys., 

 IV, 41-44. 

 Lillie, F. R. 



'19 Problems of Fertilization. The University of Chicago Press, xii + 278 

 pp. 

 Wilson, E. B. 



'03 Experiments on Cleavage and Localization in the Nemestine-egg. 

 Roux's Archiv, XVI., 411-460. 



