136 The Mechanistic Conception of Life 



formation, and R. Lillie was able to show that such eggs can 

 develop into larvae if the membrane formation is called forth 

 by raising the temperature. Von Knaffl has shown that if a 

 high temperature acts for some time on these eggs they perish 

 by cytolysis and are transformed into '' ghosts." 



We have been able to convince ourselves, therefore, that all 

 the agencies which cause cytolysis also call forth the membrane 

 formation; while the agencies which do not call forth cytolysis 

 do not cause a membrane formation. We find in addition that 

 the cytolytic power of these agencies runs parallel with their 

 power of causing membrane formation. 



From this we draw the inference that the membrane forma- 

 tion depends upon the cytolysis of the surface layer of the egg. 

 We shall see later on that we must discriminate between a 

 cortical layer and. the core of the unfertilized egg. This 

 superficial cortical layer of the egg is very thin. The essential 

 feature of the developmental stimulus consists in the cytolysis 

 of this cortical layer of the egg and this cytolysis is caused by 

 the spermatozoon. 



IV 



We have already mentioned that the cj^tolysis which under- 

 lies the membrane formation causes the development of the 

 egg, but that the egg is as a rule sickly after this membrane 

 formation. To fix our ideas provisionally we assume that 

 through the membrane formation a substance is formed which 

 must be abolished or destroyed before the egg is able to develop 

 normally. If we permit the egg to begin its development while 

 it still contains this hypothetical detrimental substance in a 

 sufficient quantity it is sickly and dies prematurely. The 

 destruction of this hypothetical substance can be brought about 

 in two ways: first, by treating the egg for a short time with a 

 hypertonic solution. When I discovered this fact there was no 

 analogue known which allowed us to draw an inference concern- 

 ing the mode of action of a hypertonic solution. I succeeded 



