FARM ANIMALS. 397 



animals is the Shetland pony, a very miniature 

 horse in his original home, but gradually in- 

 creasing in size when taken to a country of 

 liberal food supply. As an illustration of the 

 effect of climate on animals, one may observe 

 the Galloway cattle of western Scotland. They 

 have developed a remarkably heavy coat of hair 

 because of the cold and stormy weather to 

 which they have been subjected. 



Domesticated cattle receive their food with 

 very little exertion other than that of eating, 

 while the buffalo of the Western range has been 

 forced to cover considerable territory to find 

 sufficient food. This continuous exercise, along 

 with the severe weather endured, has brought 

 about the lack of thick fleshing quality and the 

 extraordinary constitution of the latter animals. 



3. The causes of Spontaneous or Extraordi- 

 nary Variation are not well understood. It is 

 known, however, that this type of variation is 

 transmitted only very irregularly. Selection 

 may be divided into two classes ; namely, natural 

 selection and artificial selection, yet the latter 

 has certain limits put upon it by the former. 



V. Selection. 



By Natural Selection is meant the repro- 

 ducing of animals most capable of self-protec- 

 tion, of subsisting and again reproducing under 

 existing conditions. It is what has been called 



