152 The Mechanistic Conception of Life 



stimulus in the activation of the egg consists in a liquefaction 

 or precipitation or some other modification of the lipoids of the 

 cortical layer of the egg which results in an imbibition or solu- 

 tion of a colloidal substance of the cortical layer. If the cyto- 

 plasm has the structure of an emulsion it is possible that lipoids 

 form the stabilizing envelope for the droplets which, according 

 to Lord Rayleigh, is necessary for the durability of the emulsion. 

 The cytolysis of the cortical layer of the egg causes its 

 development, but this development is often abnormal and comes 

 prematurely to a standstill. In order to induce a more normal 

 type of development a second agency is often required, the 

 mode of action of which is not yet so clearly understood as that 

 of the cytolytic agency, namely, a short treatment of the egg 

 with a hypertonic solution containing oxygen or a longer inhi- 

 bition of the development of the egg in normal sea-water which 

 is free from oxygen. The spermatozoon carries in addition 

 to the lysin a second substance into the egg, which acts 

 similarly to the hypertonic solution in our method of artificial 

 parthenogenesis . 



