EVOLUTION OP THE COLORS OF BIRDS. 31 



"Obviously, such a question can only be decided by 

 experiments; not, of course, experiments upon dogs and 

 cats, as Bonnet rightly remarks, but experiments upon 

 animals the tails of which are not already in a process 

 of reduction. Bonnet proposes that the question should 

 be investigated in white rats or mice, in which the 

 length of the tail is very uniform, and the occurence of 

 rudimentary tails is unknown." 



Weismann accordingly performed these experiments, 

 and there can be no doubt that they have been done in 

 a thorough and scientific manner. The result has been 

 purely negative, mice of the fifth generation bearing 

 young with the tails of normal length. Weismann, in- 

 deed, admits that these experiments do not constitute a 

 complete disproof of a possibility of transmitting mutila- 

 tions, but justly claims that, in comparison with the 

 cases of such supposed transmission occurring com- 

 pletely in a single generation, and where but one parent 

 was affected, the possibilities of transmissions were in- 

 finitely greater in his experiment. If, however, the 

 suggestion of Cunningham, that the non-inheritance of 

 mutilation in higher animals is comparable with regen- 

 eration of lost parts among lower forms, but delayed to 

 the following generation, we can easily understand that 

 while mutilations might be inherited, the contrary 

 would be the rule, and such inheritance would be due 

 to an abnormal condition of the organism. Cunning- 

 ham, furthermore, not unjustly, insinuates that even 

 the cautious Prof. Weismann may have been betrayed 

 into asserting a little more than he knew in order to 

 prove his point. For example, he says:* " Prof. Weis- 

 mann mentions the feet of Chinese ladies, which he 

 says are still, when uncompressed, as large as if the 



* Organic Evolution, Translator's Preface, p. x. 



