332 ZOOLOGY. 



that " an anatomical change is thus produced by the environ- 

 ment; and no naturalist will doubt that, if the race con- 

 tinues to multiply for a great number of years in the same 

 conditions, it will maintain its present characters or develop 

 new ones on the same lines, the more rapidly so if natural 

 selection eliminates the loss adapted individuals." 



The eggs of the English sparrow show since its intro- 

 duction into this country constant differences in size, 

 shape, and coloration from those of England (Bumpus). 



Cockerell has shown that since they have been introduced 

 into the United States the European Pieris napi has devel- 

 oped twelve and /'. rnjHB four varieties. He has also ob- 

 served that the shells of a colony of Helix neviornlis, 

 introduced into Lexington, Va., have presented a large 

 number of new and peculiar varieties not known to exist 

 in Europe. 



Animals when transported from cold or temperate 

 to warm countries soon begin to vary. In Liberia the 

 wool of both sheep and goats is very short and straight, and 

 the two kinds of animals look so much alike that tliey are 

 difficult to distinguish (Cook). In the low, warm valleys 

 of the Cordillera of South America the fleece of merino 

 sheep when not sheared falls off in flakes and is replaced 

 by a short and brilliant analogue of tliat of the she-goat. 

 The same kind of hair appears on sheep imported from 

 Europe into the West Indies and to the west coast of 

 Africa. The mastiff and goat of Thibet carried from the 

 lofty plateau of tlie Himalaya to Cashmere also lose their 

 fine wool. In Colombia the adult hens lose their jilumes. 

 The Carib or tropical variety of dog is hairless. Oats at 

 Mombasa, on the east coast of Africa (lat. 4^), have short, 

 stiff' hair instead of fur; and a cat from Algoa Bay when 

 left only eight weeks at Mombasa underwent a com])lete 

 metamorphosis, having parted with its sandy-colored fur 

 (Morgan). 



Cold has naturally the inverse etfect. Mammals with 

 short and smootli hair transpurted from tlie tropics to the 



