VARIATION. 317 



good illustrations of climatic influences. These animals in 

 their native land have to rough it and are exposed to a 

 rugged climate. When introduced into other countries, where 

 they are more liberally fed and better housed, they lose their 

 rugged coats and increase in size. 



Variation as treated thus far might properly be designated 

 as natural variation. We have another kind which sometimes 

 manifests itself in another form; a rather unusual form, 

 and is called spontaneous variation. 11, differs from natural 

 or ordinary variation in that it is much more marked 

 and usually confined to individuals rather than to a 

 number of animals in a herd or breed. Natural variation 

 usually is recognized as a slight change in form, color, or 

 some other point, and generally affects a number of animals 

 in a herd or breed. Spontaneous variation is more marked 

 in its influence and less general in its distribution, as in 

 many instances not more than one animal may be affected 

 in a herd. It is in a measure something over which the 

 breeder has no control. It usually comes as a surprise and 

 cannot be easily accounted for. Some claim that it is due 

 to a severe shock given to the mother, or mental impres- 

 sions at the time of conception, or during the early stages 

 of pregnancy. These influences do not, however, explain all 

 the cases which occur. Some illustrations along this line 

 might be cited. A calf with six legs, or two heads, would be 

 a good illustration. A rabbit with one ear, any radical varia- 

 tion in color, such as a red Aberdeen Angus, and so on, would 

 belong to this class. On account of the infrequency with 

 which these variations occur, they seldom if ever perpetuate 

 themselves. 



Natural variation is one of the most important factors under 

 the control of man in the higher development of our animals. 

 By means of this law man has accomplished much, and by a 

 thorough understanding of the same and its application he can 

 still do a great deal towards the betterment of our domesti- 

 cated animals. 



