298 E. E. JUST. 



treatment the over-exposed egg cytolyzes. The rate of cytolysis, 

 however, is so different that we must regard the process of dif- 

 ferent order in the two cases. 



Over-exposure to butyric acid is cytolytic; hence, the egg 

 rapidly dies, the cortical thickening is the beginning of cytolysis. 

 In the case of the activated egg, cytolysis is entirely secondary ; 

 cytolysis takes place in spite of activation not because of it. 

 Moreover, that which first cytolyzes in the over-exposed egg, 

 namely the cortex, is absent in the activated egg because it has 

 liquefied. Therefore, the cytolysis in the two eggs is quali- 

 tatively different. 



For these reasons, therefore, we must conclude that the over- 

 exposed egg is a cytolysing egg but that activation is not a 

 cytolysis. 



But since according to Loeb all activation is caused by a 

 " superficial " cytolysis we must examine further his widely 

 accepted theory. 



A. The Cytolysis Theory of Loeb. 



In his book " Artificial Parthenogenesis and Fertilization," 

 Loeb tells us : " The object of these experiments was the substi- 

 tution of physico-chemical agencies for the mysterious complex 

 ' living spermatozoon.' ' ' This book gives a survey of the 

 methods by which the unfertilized egg can be caused to develop 

 into an embryo and the conclusions which can be drawn concern- 

 ing the mechanism by which the spermatozoon produces this 

 effect. The theory which the author published in 1905 and 1.906 

 that at least two factors are involved in this process, namely, one 

 which brings about a change in the surface of the egg (the essen- 

 tial factor) and a second, corrective factor, seems to explain all 

 the phenomena observed in the new territory and has proved a 

 reliable guide." Thus Loeb despite his numerous other sugges- 

 tions as to the cause of development quite definitely commits 

 himself to the cytolysis theory that the egg either by the " mys- 

 terious complex living spermatozoon " or by the " substitution of 

 physico-chemical agencies " develops through a change in its 

 surface which he calls " superficial cytolysis." Against this 

 theory of activation several potent objections may be raised. 



