332 Mr. G. A. K. Marshall on Birds as a Factor in the 



from India (Proc. Ent. Soc, 1897, p. xxxviii) ; Commander 

 J. J. Walker and Col. Yerbury (I.e. p. xxxix); J. C. 

 Kershaw, from S. China (Trans. Ent. Soc, 1905, p. 6); 

 Paul Hahnel, from Tropical S. America ("Iris," 1890, pp. 

 810-321) ; while Packard has quoted the opinions of a 

 number of his North American correspondents to the same 

 effect, and has generally reviewed the whole subject in a 

 sense adverse to the theory of mimicry in a very able paper 

 entitled " Origin of Markings of Organisms " (Proc. Amer. 

 Phil. Soc, 1904', pp. 393-450), a paper which has been 

 excellently criticised in our Proceedings for 1906 (p. xxxvii) 

 by Eltringham. 



The evidence adduced by these authors is necessarily of 

 a purely negative character, being always to the effect that 

 each of them has collected or observed butterflies for a 

 shorter or longer period and yet has not seen any, or at 

 most very few, cases of birds eating butterflies. In dealing 

 with the theories of mimicry most of them are content 

 with a purely destructive criticism, and make no attempt 

 to explain the mass of facts which has now been ac- 

 cumulated by Professor Poulton and his correspondents. 

 Others, such as Hahnel, Skertchley, Eimer, etc., have 

 attempted to suggest alternative theories to explain these 

 striking phenomena. Unfortunately some of the critics 

 have not even taken the trouble to grasp the real nature 

 of the suggestions which they criticise (this is especially 

 true of Fritz Miiller's views) ; and while they unite in 

 condemning the theories of mimicry on the ground that 

 they involve too many assumptions for which there is no 

 experimental evidence, it is noticeable that this criticism 

 applies with even greater force to their own hypotheses, 

 quite apart from the far graver objections which may be 

 raised against all of them. The vague suggestion that 

 mimetic resemblances are all due to the direct action of a 

 similar environment furnishes an excellent example of the 

 ill-digested and wholly inadequate conceptions which pass 

 current among many entomologists who have not made 

 themselves acquainted with the mere rudiments of the 

 subject. But it is not my purpose to discuss these 

 questions here. For in the first place, I am by no means 

 prepared to accept the fundamental assumption which 

 underlies all these alternative interpretations, namely, that 

 at the present time the influence of birds upon butterfly 

 coloration is a negligible quality ; and secondly, because 



