160 MR. C. X. BARKER 



That yariation i>s governed by heredity, and its direc- 

 tion influenced by physical causes such as those of habits 

 and enyironment, and, finally, that the duty of natural 

 selection is somewhat like that of the public hangman 

 who executes those ^yho do not conform to these rules of 

 nature ! 



That nature as often achieves her purpose in the per- 

 petuation of species by hardihood and prolificness as by 

 any other specialized form of protection. 



That nature is a huge scheme Qf compensation balances, 

 some of the details of which we can only guess at. 



Addendum. 



Since writing my paper on " Mimicry by Natural Selec- 

 tion," it has been suggested to me that I have not re- 

 ferred to any of the more recent literature on the sub- 

 ject. Most of this was not available to me at the time, 

 but through the kindness of a friend, I have since re- 

 ceived a good deal of interesting matter on this absorb- 

 ing subject. I have had the pleasure of reading the dis- 

 cussions raised by the publication of Professor Punnett's 

 book on '' Mimicry in Butterflies," and I have studied 

 the book itself. The following are a few comments upon 

 what I have read, and how they appeal to me as :i free 

 lance : — 



The aggregate results still leave me far from satisfied, 

 upon the one point, which I consider vital to the whole 

 theory of " Mimicry by Natural Selection," for it is the 

 very foundation upon which the whole superstructure 

 rests. It is hardly necessary to say that I allude to the 

 discriminating persecution of butterflies by birds. Mr. 

 Swynnerton (Ibis, 1912) gives some further evidence in 

 support of the attacks of birds on butterflies, but a great 

 deal of his paper is devoted to the results of experiments 

 in feeding captive birds, which, in my opinion, are un- 

 reliable tests as to the habits of wild birds. Per contra, 

 there is much data froin Col. Manders (Trans. Ent. Soc , 

 Lond., 1911), Mr. Freyer (Proc. Zoo. Soc. 1913), and 



