( Ixix ) 



absence of work in this direction. I am glad to say, how- 

 ever, that, thanks to the zeal of our distinguished Fellow, 

 Mr. Francis Galton, there is some prospect of this want 

 being supplied at no very distant future. From the theoretical 

 side, Dr. A. R. Wallace's ingenious treatment of this problem 

 is doubtless familiar to all who have considered the question.* 



It seems necessary to apologise for occupying your time 

 wdth this recapitulation of old and well-worn topics. But in 

 the discussion at the Linnean Society, and subsequently in 

 " Nature, "t the whole question of the utihty of specific 

 characters, and with it the interpretation of the principles 

 of the selection theory, has again been raised. The question 

 is of supreme importance to entomologists, because the diffi- 

 culties which have prevented many workers in our subject 

 from accepting natural selection as a sufficient cause of species 

 transformation, appear to me to be largely, if not entirely, 

 due to the meaning of the term " utility " as applied to 

 specific characters. In fact, the various opinions expressed 

 by those who have taken part in the discussion, resolve 

 themselves into a few very simple questions : Are the 

 systematic characters by which species are diagnostically 

 separated from one another, those characters which, accord- 

 ing to the theory of natural selection, have given their 

 possessors that advantage in the struggle for life which has 

 led to their survival ? Are the external, visible, appreciable, 

 measurable characters alone to be regarded as of selection 

 value ? May not some at least of the minor, more or less, 

 constant " specific " characters be the outward expression of 

 some constitutional or physiological differences at present 

 beyond the power of our methods of discrimination ? 



The chief objection which has been urged against this last 

 view is that it necessitates the extension of the meaning of 

 the term " correlation " beyond that originally assigned to it 

 by Darwin. Even if this were the case I do not, for the 

 reasons already stated, attach much weight to objections of 

 this class. If Darwin in his time did not contemplate cor- 



* " Darwinism," pp. 173-179. See also a letter by the writer, in " Nature," 

 1886, Vol. XXXI v., p. 3^. 

 t 189J, Vol. LI v., pp. 245, 293, 342, 365, 413, 435, 460, 491, 529, etc. 



