674 ZOOLOGY. 



exjiosed to humiiii interference may vary when subjected to 

 changes in their environment. Also the fact that man can, by 

 careful selection, breed races of horses adapted for draught, 

 speed, or the road ; races of cows for difEerent qualities of 

 milk ; beeves for meat ; races of sheep for pre-eminence in 

 the quality of their wool or mutton, or races of doves or 

 poultry for beauty, usefulness, or other qualities ; the fact 

 that gentleness, and generally good mental qualities, can be 

 made to replace viciousness in horses, cattle, dogs — all these 

 and many other facts, in the art of breeding animals known 

 to fanciers, indicate that nature has, through the past ages, 

 by the operation of natural laws, evolved races and species 

 of animals which have followed constantly improving lines 

 of development, the outcome of which are creatures the best 

 fitted to withstand the struggle for existence, the most use- 

 ful in the scheme of nature, and the most in harmony with 

 the world about them. Progress, on the whole, therefore, 

 has been beneficent, the best proof of which is the last 

 product of evolution, man, the paragon of creation. 



