146 The Mechanistic Conception of Life 



the cortical layer of the egg and thereby causes development. 

 The greater tendency of the eggs of certain animals for spon- 

 taneous parthenogenetic development thus depends upon the 

 relatively small degree of durability of the emulsion which 

 constitutes the cortical layer of the egg. But it should be 

 stated that this hypothesis is not essential for the lysin theory 

 of the activation of the egg. 



VIII 



The assumption that the membrane formation is only a 

 superficial cytolysis of the egg presupposes that the cortical 

 layer of the egg is different from the rest of the cytoplasm. 

 Biitschli had already reached such a conclusion on the basis 

 of histological observations. I am inclined to accept this view 

 on the basis of my observations on the action of cytolytic 

 agencies on the unfertilized egg. The action of these agencies 

 on the unfertilized egg always occurs in two stages which are 

 often separated from each other by a considerable interval of 

 time. The first stage is the cytolysis of the superficial layer; 

 the second stage is the cytolysis of the rest of the egg. This 

 is most obvious in experiments with weak solutions of saponin 

 or solanin in sea-water. In this case first a membrane forma- 

 tion occurs, then a pause ensues, often of several minutes, and 

 then cytolysis of the whole egg follows. If instead of saponin 

 benzol is used a pause can also be observed between membrane 

 formation and cytolysis of the whole egg but this pause is short, 

 often only a fraction of a second, or at the best a few seconds. 



It can also be shown directly that there is a qualitative 

 difference between the cortical layer of the protoplasm and the 

 rest. If for the artificial membrane formation the lower fatty 

 acids, from the formic to the capronic acid, are used, cytolysis 

 of the cortical layer only is observed, i.e., membrane formation 

 follows but no cytolysis of the whole egg. If, however, the 

 higher fatty acids of the same series from the heptylic acid on 



