268 PSEUDACRAEA EURYTUS 



those of 1918-19 ; and also those that had learnt their 

 lesson in 1914 must be supposed to have unlearnt it in 

 1918, when the models which they had known to be 

 distasteful were no longer to be seen. If this be so, then 

 it must be further supposed that birds need to refresh 

 their memories at intervals during adult life. 



These numerous and beautifully graded transitional 

 forms of one species are quite consistent with the explan- 

 ation of mimicry being produced and maintained by 

 the continuous operation of Natural Selection upon small 

 variations. 



But at first sight they do not seem to be at all in con- 

 formity with the theory of the production of mimics by 

 Mutations — that is, sudden large variations which appear 

 complete all at once and never revert to the form of the 

 parent. Indeed, the writings of such an exponent of 

 the Mutation theory as Professor Punnett seem at first 

 sight to support this argument, that the intermediates 

 are a difficulty in the way of the Mutationist. 



Thus, in the 5th edition of Mendelism, 1919, he dis- 

 cusses two forms of an interesting species of Euralia, a 

 Nymphaline of which the form wahlbergi mimics Amauris 

 niavius dominicanus, and the form mima mimics Amauris 

 echeria. On p. 177 Professor Punnett says: "According 

 to Mendelian views, on the other hand, the dominicanus 

 pattern arose suddenly from the echeria pattern (or vice 

 versa), and similarly wahlbergi arose suddenly from mima. 

 . . . On the modern Darwinian view natural selection 

 gradually shapes mima into the wahlbergi form owing to 

 the presence of dominicanus ; on the Mendelian view 

 natural selection merely conserves the wahlbergi form 

 when once it has arisen. Now this case of mimicry is 

 one of especial interest, because we have experimental 

 evidence that the relation between mima and wahlbergi 

 is a simple Mendelian one, mima here being the dominant 

 and wahlbergi the recessive form. The two have been 



