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Diaposematism, with reference to some Limitations of the 



[xiv 

 Miillerian Hypothesis of Mimicry." In this he pointed out 

 the difficulty of accepting the idea of a mutual simultaneous 

 mimicry between two unpalatable species, such as is postulated 

 by the hypothesis of Diaposematism. It was suggested that 

 an initial inequality in the individual numbers of the two dis- 

 tasteful species was an essential condition for the production 

 of Miillerian mimicry, and that in such circumstances the 

 mimetic approach would always be in one direction only, 

 namely, from the rarer species towards the more abundant ;. 

 for any initial variation from the latter towards the former 

 must be disadvantageous. The various cases which have been 

 put forward as proving the existence of Diaposematism in 

 nature were critically examined, and it was contended that 

 the facts could be more satisfactorily interpreted on lines 

 which did not involve the assumption of a mutual interchange 

 of characters between mimic and model. While the great 

 importance of Miiller's principle was fully recognised, it was 

 pointed out that it had certain definite limitations, and the 

 attempt to explain all cases of mimicry among butterflies on 

 this theory was contested. On the other hand, it was held 

 that the wide significance of Bates' principle had not been 

 adequately appreciated, and it was urged that this theory 

 would afford an explanation of many cases of mimicry between 

 unpalatable species, which had been previously considered as 

 purely Miillerian in character. 



Professor E. B. Poulton, F.R.S., said that at that late hour it 

 was impossible to reply to the details of Mr. Marshall's paper,, 

 and that any real discussion of the questions raised by him 

 must be deferred to a future occasion. He would therefore 

 take some other opportunity of exhibiting the specimens 

 which he had specially selected with reference to Mr. Mar- 

 shall's arguments. He had, however, just received a letter 

 from Mr. S. A. Neave, F.ES., in the Congo Free State, 

 which, by a curious coincidence, bore upon this very dis- 

 cussion of the relative importance of the Batesian and 

 Miillerian hypotheses. He was anxious that Mr. Neave's 

 observations should appear at once in the Proceedings, and 



