106 THE NATURE OF LIFE 



the weaker germ cells are injured or 

 killed by the alcohol. The stronger are 

 uninjured or may possibly be stimulated. 

 In any case there is a rapid elimination 

 of the weaker and in the fourth genera- 

 tion a superior strain results. It should 

 be understood that the alcohol is applied 

 to the parents of the first generation only, 

 the four subsequent generations receiv- 

 ing no alcohol. In the experiments of 

 Pearl on chickens this improvement oc- 

 curred much more rapidly. 



A more permanent effect was obtained 

 by Guyer by introducing materig-l from 

 the eye of the rabbit into fowls where 

 it caused the production of a substance 

 which was injected into the rabbit and 

 caused the offspring of the latter to 

 have defective eyes. It is well known 

 that the introduction of foreign protein 

 causes the body to produce substances 

 which tend to destroy or precipitate that 

 protein and it is possible that a body of 

 this sort is responsible for the effects ob- 

 tained. If the fowl produced a sub- 



