( cvii ) 



observes, " it is indubitable that external influences such as 

 those emanating from the environment or media in which 

 the species live, are able to cause direct variation of the 

 germ plasm that is permanent because hereditary." 



But when the effects on the individual are only transient 

 there would still remain scope for the great factor in evolution, 

 natural selection, because the tendency to respond in general 

 colouring to the temperature undoubtedly varies, and, if it 

 be protective, an individual ready to respond in this way 

 would have an advantage which natural selection could secure 

 to the species. 



Two varying aspects of Nature. 



But, do we find any correspondence between the colouring 

 produced by high and low temperatures respectively on 

 Lepidoptera and the general colouring of those found in warm 

 and cold countries respectively? I think Ave do.* I have 

 looked through some of the families genera and species that are 

 spread over cold regions as well as over temperate and warmer 

 parts, among them Argynnids and Satyrids, in the Natural 

 History Museum at South Kensington, and they seem to me to 

 show the following results. In those from very cold regions 

 the ground colour tends to a uniform dulness with sparseness 

 or diminution in size of scales, and consequent "greasy" 

 appearance, owing to the shining membrane of the wings 

 showing between the scales, and paucity or indistinctness or 

 want of force in the markings. In those taken in what may 

 be described as the cold temperate regions, there is a greater 

 tendency towards bright light brown ochreous or fulvous, the 

 sort of colour so very common in butterflies, shown for exam- 

 ple by the bright parts of the wing of Pararge megsera, or the 

 female of Epinephih jurtina, and to greater variety of marking. 

 In those from the warmer temperate countries there is an 



* P. cardui is much darkened by exposing the pupa to a low tempera- 

 ture. On the other hand, specimens placed at a high one have a beautiful 

 light brown golden hue extending over much the greater part of the hinder 

 wings and a large part of the forewings. but without a trace of the rosy 

 colour on the upper wings which gives such a charm to ordinary English 

 examples when fresh. I was interested in seeing by a notice in the Ent. 

 Eecord, vol. xii, p. 156, that an African type is much less rosy than the 

 ordinary European form. 



