( cviii ) 



increased tendency towards brightness in place of sombreness, 

 and an increasing variety of marking and colour. My know- 

 ledge, however, of the butterflies of the world is so limited that 

 I should have distrusted my own conclusions had I not found 

 support for them in the opinions of several others better 

 acquainted with the subject whom I have consulted. Perhaps 

 on this point I may refer to the remarks of your former Pre- 

 sident, Lord Walsingham (Proc. of Ent. Soc. 1890, p. liv), 

 where he speaks of the general tendency of Arctic Lepidoptera 

 to a certain suffusion of markings and to an increase in the 

 proportion of dull and dingy scales.* 



But, whether it is owing to the direct effect of temperature 

 on the individual, or whether it is fixed by natural selection as 

 being transmissible and of protective value, or whether there is 

 a combination of these causes and perhaps others, I think 

 there is no doubt that in temperate countries as a general rule 

 the southern species and the summer broods do in their general 

 colouring vary rather in the direction of light brown, and the 

 more northern species and the spring broods in the direction 

 of darker colouring. 



And now let me conclude with a few words of apology for 

 the many imperfections arising from my want of knowledge 

 on points beyond those which I have found opportunity per- 

 sonally to investigate. I think you can rely on my state- 

 ments of fact, culled from a very large number of experiments, 

 the results of which, however, as a whole, I have not yet had 

 time to co-ordinate, and one can hardly either gather or put 

 forward the facts without some attempts to explain them. As 

 to my ventures in this direction, they may serve as materials for 

 the consideration of others better capable of dealing with such 

 a subject. I hope what I have put forward may be acceptable 

 as a contribution, however slight, to the elucidation of some 

 interesting phases in that perennial conflict between the phylo- 

 geny of the organism and its environment which prevails 

 wherever there is life, the ceaseless struggle by which nature 



* There seems an exception in the colour orange which is so highly 

 developed in some of the Argynnids of the Arctic circle ; it seems a 

 brighter kind of orange, however arrived at, from that, reached through light 

 qrown referred to at p. civ. 



