( Ixxxiii ) 



effect thus produced upon the pupal physiology finds visible 

 expression in the colour and form of the imago. I may 

 call attention, in connection with this point, to a very valu- 

 able contribution to the physiology of wing pigments in 

 Lepidoptera, by Mr. A. G. Mayer, who has recently shown 

 that the pigments of the scales are derived from the blood 

 (hasmolymph) of the pupa.* If, therefore, any systematist 

 asks of what use it can be to a butterfly or moth to have a 

 winter form of a different size, colour, and pattern to the 

 summer form, an answer might be suggested on the above 

 grounds. And if, further, the adaptability of the pupal physio- 

 logy makes itself manifest in this way in the imago, why 

 should we not regard permanent climatic change as a pos- 

 sible cause of species transformation through this same 

 process of physiological adaptation?! 



The question of the utility of specific characters in the 

 form that it has assumed of late years, appears to me to be 



forms are not modified for direct protective purposes (Weismanu's " direct 

 seasonal dimorphism " ; see this author's "New Experiments on the 

 Seasonal Dimorphism of Lepidnptera," Eng. Ed. from " Entomologist," 

 p. 37, et seq.). When temperature changes induce modification in 

 species which are not ordinarily seasonally dimorphic, t'len the influence 

 maybe ascribed either to reversion or to '' dirjct aotioit " on physiological 

 function. But the latter could not (on Weismannian pi-inciples) give rise to 

 permanent seasonal dimorphi-i^m (it required by the species) unless the 

 physiological modification corresponded with some increased fitness for a 

 higher or lower temperature, in which case selection would act in the usual 

 way. Perhaps this is what Standfuss had in mind when he says : — " These 

 experiments give rise to phylogenetic forms ; forms, that is, which are no- 

 where to be found on the earth at the present day within the compass of the 

 species, but which may either have existed in past epochs, or may, perhaps, 

 be destined to arise in future "(•' Entomologist," May, 1895, p. 146). In 

 other words, the physiological disturbance induced Vjy temperature change 

 produces results in the imago which may furnish the raw material for a visible 

 seasonal dimorphism in the future or which have already been made use of 

 for this purpose in the paot, tue lost character reappearing when the physio- 

 logical processes are submitted to the same influenje as that under which 

 they were developed. 



* "Bull. Mus. Comp. Zoo. Harvard Coll.," Vol. XXIX., pp. 211— 23G, 

 No. 5, June, 1890. 



t After the above was in type I was made aware by Mr. J. W. Tutt, that 

 he had stated similar views before the City of London Entomological Society 

 on Dec. 1st, 189G. I was, of course, ignorant of this at the time of writing, 

 and I am indebted to Mr. Tutt for forwarding me advanced proofs of his 

 address. It is to me interesting to find that we have arrived by different 

 roads at somewhat similar conclusions. 



