202 Address to the British Association 



cayenne pepper with, canaries, and hempseed with parrots — 

 are notorious. The direct action of the environment on 

 organisms has, I think, been of late somewhat undervalued. 

 Amongst evidences in favour of its importance, I would refer 

 to some of Mr. Alfred Wallace's observations.^ He tells us 

 that in the small island of Amboina, the butterflies (twelve 

 species, of nine different genera) are larger than those of any 

 of the more considerable islands about it, and that this is an 

 effect plainly due to some local influence. In Celebes, a 

 whole series of butterflies are not only of a larger size, but 

 have the same peculiar form of wing. The Duke of York's 

 Island seems, he tells us, to have a tendency to make birds 

 and insects white, or at least pale, and the Philippines, to 

 develop metallic colours, while the Moluccas and New 

 Guinea seem to favour blackness and redness in parrots and 

 pigeons. Species of butterflies which in India are provided 

 with a tail to the wing, begin to lose that appendage in the 

 islands, and retain no trace of it on the borders of the Pacific. 

 The JEneas group of Papilios never have tails in the equa- 

 torial region of the Amazon Valley, but gradually acquire 

 tails, in many cases, as they range towards the northern and 

 southern tropics. Mr. Gould says that birds are more 

 highly coloured under a clear atmosphere than in islands or 

 on coasts — a condition which also seems to affect insects, 

 while it is notorious that many shore plants have fleshy 

 leaves. I need but refer to the English oysters mentioned 

 by Costa, which, when transported to the Mediterranean, 

 grew rapidly like the true Mediterranean oyster ; and to the 

 twenty different kinds of American trees, said by Meehan to 

 differ in the same manner from their nearest European 

 allies, as well as to the dogs, cats, and rabbits which have 

 been proved to undergo modifications directly induced by 

 climatic change. 



1 See Tropical Nature, pp. 254-259. 



