THE SELECTION OF ANIMALS 33 



the second class are the unalterable conditions that apper- 

 tain to the contour of certain soils, to the unremovable ob- 

 structions to tillage found in them, and to the degree of 

 their exposure, climatic influences also included. 



The power of environment to produce modification, 

 sometimes almost imperceptible and again more quickly, is 

 so great as to be in a sense irresistible. It is one of those 

 mighty forces that work in silence. The rapidity of the 

 modification produced is proportionate to the intensity of 

 the changed conditions to which the animals are subjected. 

 Nature unassisted at length brings to that level which the 

 natural conditions of soil and climate can maintain, the 

 animals subjected to such environment, and man can mod- 

 ify the results by the extent to which he resorts to artificial 

 conditions when caring for them. 



Natural environment may exercise an influence in 

 the direction of increase or decrease according to its 

 nature. Illustrations of the former are found: (i) in the 

 greater size of Southdown sheep on rich prairie lands, than 

 of the same on their native downs in England; (2) in the 

 wonderful hardihood of Sable island ponies and of certain 

 sheep bred on islands off the coast of Maine and (3) in the 

 great powers of endurance of the average horse bred for 

 generations on the range. Illustrations of the latter are 

 found : ( i ) In the decreased size of the Lincoln sheep 

 brought to hill pastures; (2) in the decrease of bone, size, 

 stamina and breeding qualities of swine kept for genera- 

 tions in the corn belt of the United States and (3) in the 

 lessened hardihood of West Highland cattle long sub- 

 jected to artificial conditions. 



Selecting animals for breeding without due reference to 

 environment is a mistake that is all too common, and it is a 

 mistake in all instances costly in proportion to the extent to 

 which the conditions of environment have been violated in 

 the choice. The breeder who attempts to rear Shorthorns 

 on pastures only fit to sustain the small Devons under- 

 takes the task of the engine which draws a heavy train 



