100 Artificial Parthenogenesis 



action of the two agencies upon the development of the 

 egg. It soon became obvious that the membrane 

 formation (or the alteration underlying membrane 

 formation) was the more important of the two, since in 

 the eggs of starfish and annelids this was sufficient for 

 the production of larvae ; and that the second treatment 

 had only the corrective effect, of overcoming the sickly 

 condition in which mere membrane formation had left 

 the eggs. It was, therefore, of great interest to ascer- 

 tain what substances or agencies caused membrane 

 formation in the egg, since it now became clear that 

 the spermatozoon could only cause membrane formation 

 by carrying one such substance into the egg. These 

 investigations led the writer to the result that all those 

 substances and agencies which are known to cause 

 cytolysis or hemolysis (see Chapter III) will also induce 

 membrane formation, and that the essential feature in 

 the causation of development is a cytolysis of the 

 superficial or cortical layer of the egg. As soon as 

 this layer is destroyed the development of the egg can 

 begin. 



The substances and agencies which cause cytolysis and 

 hence, if their action is restricted to the surface of the 

 egg, will induce development are, besides the fatty acids : 

 (i) saponin or solanin or bile salts; (2) the solvents of 

 lipoids, benzol, toluol, amylene, chloroform, aldehyde, 

 ether, alcohols, etc.; (3) bases; (4) hypertonic or hypo- 

 tonic solutions; (5) rise in temperature, and (6) certain 



