( liv ) 



the conclusion he comes to has been indicated up to the 

 present time, he seems to declare in favour of the theory that 

 such varietal changes are due to the action of moisture. A 

 valuable paper was read by Mr. Merrifield at one of our last 

 meetings, giving an account of some interesting experiments 

 carried out upon the pup© of certain Geometj-idte, in which 

 the temperature was artificially raised or lowered, excess of 

 cold producing the darker coloration of the winter brood, with 

 the reverse effect under the opposite conditions. Mr. Merri- 

 field's experiments were entirely conducted with seasonally 

 dimorphic forms, as also were those of W. H. Edwards and 

 Weismann, and although the power of producing artificially 

 certain recognised varieties was still questioned by some of 

 those who heard him, I think his carefully conducted re- 

 searches went sufficiently far to prove that retardation of 

 development does produce a tendency to darker colouring 

 where such colouring is distinctly seasonal. Nevertheless it 

 must be remembered that no attempt has yet been made to 

 establish by experiment any theory that variation in the 

 direction of melanism can be encouraged in insects not 

 seasonally dimorphic, but subject to such variation under 

 natural climatic conditions. 



Mr. Tutt, referring to a paper of my own in which I called 

 attention to the tendency to melanism exhibited by Arctic 

 and Alpine Lepidoptera, points out that insects from high 

 latitudes are not generally melanic. I think I may at once 

 admit that I had used the term "melanic" somewhat in- 

 correctly in this connection ; what I desired to point out was 

 the general tendency of Arctic Lepidoptera to a certain 

 suffusion of markings, and to an increase in the proportion 

 of dull or dingy scales calculated more rapidly to absorb 

 heat than the purer white of more southern varieties. Such 

 a tendency will, I think, be admitted to exist, but I am aware 

 it is far more conspicuous in many insular and alpine 

 districts ; and while I cannot agree that the arguments put 

 forward in that paper are in any way undermined by this 

 admission, or that the advantage secured to the species by 

 the development of colour capable of rapidly absorbing heat 

 has been in any way disproved, I am quite willing to accept 



