ANIMAL BIOLOGY 



result that now our better breeds of cattle produce several 

 times as much milk as did the cattle of a few centuries ago. 

 The selections of the pigeon fancier have resulted in the 

 production of such diverse types as the pouter, the fantail, 

 the tumbler and numerous other varieties, all of which are 

 considered to be the descendents of the original rock pigeon 

 Columba lima. Our domestic dogs doubtless sprang from 

 several varieties of wolf, but cross breeding and continued 

 selection have resulted in the production of the greatest 

 variety of form, size and disposition. Animals so different 

 as the bull-dog, the greyhound, the newfoundland, the 

 spaniel, and fehe terrier would undoubtedly have been 

 considered members of very distinct species, if not genera, 

 had they been met with in a state of nature. This process 

 of artificial selection, as it is called, has resulted also in the 

 production of many varieties of plants which are of the 

 utmost value to man. By its means man has greatly 

 increased the quality and yield per acre of his wheat, oats, 

 corn and many other grains, and produced countless 

 varieties of beautiful flowers. The genius of Luther 

 Burbank has given us a stoneless plum, a spineless cactus, 

 the Burbank potato and a large number of other improved 

 varieties of fruits and vegetables, as well as ornamental 

 plants. 



The possibility of improving our races of plants and 

 animals depends upon the occurrence of variations which 

 are inherited. Variations occur in a state of nature as 

 well as under domestication, and if there were any agency 

 capable of selecting variations of a certain type, organisms 

 would be modified in nature just as they have been under 

 domestication through the agency of man. The existence 

 of such a modifying agency was first pointed out by Charles 

 Darwin and Alfred Russel Wallace who independently 

 and at nearly the same time worked out their celebrated 



