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involves the conception of a mutual simultaneous approach on 

 the part of two species. Indeed, from the last-quoted 

 definition, we may legitimately infer, that whatever he may 

 think now. Dr. Dixey then considered that simultaneous 

 approach was the natural consequence of that give-and-take 

 interchange which his hypothesis postulates ; and the whole 

 internal evidence in his papers is in accord with that view. 



"Then as to the claim that Alternating Mimicry is 

 practically the same thing as Reciprocal ]\Iimicry. This is a 

 statement which I am entirely unable to accept. Throughout 

 Dr. Dixey's writings I can find no trace whatever of the 

 conception of Alternating Minicry as I have defined it above. 

 It has been seen that this conception is based entirely on the 

 view that the relative number of individuals is the most 

 important factor in determining the direction of the mimetic 

 approach between any two species of equal inedibility. Yet 

 Ixxiii] 



this question of relative numbers has been entirely neglected 

 by Dr. Dixey in dealing with his supposed cases of mimetic 

 interchange. How can he explain this strange omission if 

 Alternating Mimicry was really an essential portion of his 

 hypothesis as he suggests *? It is difiicult also to understand 

 how he could have made the following assertion : ' It seems 

 hitherto to have been taken for granted that a dominant form 

 will attract or retain other species within its own sphere of 

 influence, without being itself attracted in return ; w^hereas 

 the fact is, as we have seen, that each member of an inedible 

 association has more or less influence upon all the rest ' {op. 

 cU. 1897, p. 327). Now I do not at all accept the validity of 

 this theoretical ' fact,' and it is quite at variance with the 

 principle which underlies the suggestion of Alternating 

 Mimicry. One final quotation will suflice. We have been 

 told that ' the most complete intermingling of characters 

 given and taken on both sides may be expected when two 

 species meet on equal terms, neither being strong enough to 

 predominate over the other' (I. c). This then is considered 

 to be the optimum condition for the production of Reciprocal 

 Mimicry, and it is obvious that any possibility of Alternating 

 Mimicry is entirely excluded ; indeed, from the standpoint of 

 that hypothesis there would be no mimicry at all in such a 



