320 STUDIES IN GENERAL PHYSIOLOGY 



development of an embryo would, according to this, be in a 

 physiologico-chemical sense an epigenesis and no evolution. 

 In order to test this idea, I made experiments on the rela- 

 tive sensitiveness of the embryo in the various stages of its 

 development. I thought that sudden changes in the sensi- 

 tiveness during the transition from one developmental stage 

 to another would speak for epigenesis. Such a change in 

 reaction was, indeed, found in the experiments on loss of 

 water. 



I have begun experiments similar to those on Fundulus 

 on Perca fluviatilis. The physiological reactions of the 

 embryo of Perca are, however, very different from those of 

 Fundulus, as was to be expected from the beginning 



