94 DARWINISM chap. 



of the scutellse also vary. The eggs also vary somewhat in 

 size and shape ; and the amount of downy clothing on the 

 young bird, when first hatched, differs very considerably. 

 Finally, the attitude of the body, the manner of walking, the 

 mode of flight, and the voice, all exhibit modifications of the 

 most remarkable kind.^ 



Acclimatisation. 



A very important kind of variation is that constitutional 

 change termed acclimatisation, which enables any organism to 

 become gradually adapted to a difterent climate from the 

 parent stock. As closely allied species often inhabit di3"erent 

 countries possessing very different climates, we should expect 

 to find cases illustrating this change among our domesticated 

 animals and cultivated plants. A few examples Avill therefore 

 be adduced showing that such constitutional variation does 

 occur. 



Among animals the cases are not numerous, because no 

 systematic attempt has been made to select varieties for this 

 special quality. It has, however, been observed that, though 

 no European dogs thrive well in India, the Newfoundland dog, 

 originating from a severe climate, can hardly be kept alive. 

 A better case, perhaps, is furnished by merino sheep, which, 

 when imported directly from England, do not thrive, while those 

 which have been bred in the intermediate climate of the Cape 

 of Good Hope do much better. When geese were first intro- 

 duced into Bogota, they laid few eggs at long intervals, and 

 few of the young surAdved. By degrees, however, the fecundity 

 improved, and in about twenty years became equal to what 

 it is in Europe. According to Garcilaso, when fowls were 

 first introduced into Peru they Avere not fertile, Avhereas now 

 they are as much so as in Europe. 



Plants furnish much more important CAadence. Our 

 nurserymen distinguish in their catalogTies varieties of fruit- 

 trees Avhich are more or less hardy, and this is especially the 

 case in America, Avhere certain varieties only Avill stand the 

 severe climate of Canada. There is one variety of pear, the 

 Forelle, Avhich both in England and France Avithstood frosts 



^ This account of domestic iiigeons is greatly condensed from Mr. 

 Darmn's work already referred to. 



