ITS PLACE IN NATURE 



8 



studied by everyone who wishes to gain an insight 

 into some of the fundamental principles of biology. In 

 scarcely any other animal has specialisation of various 

 parts — that is, modification from the general or average 

 type to conform to the requirements of some special 

 mode of existence — been carried to such an extreme. 

 In many organs, but especially in the limbs and teeth, 

 we find the strongest evidence of two opposing prin- 

 ciples striving against each other for the mastery in 

 fashioning their form and structure. We find 

 heredity, or adherence to a general type derived from 

 ancestors, opposed by special modifications of or devia- 

 tions from that type, and the latter generally getting 

 the victory, although in the numerous rudimentary 

 structures that remain there is significant evidence of 

 ancestral conditions long passed away. The various 

 specialisations, evidently in adaptation to purpose, will 

 be thought by many to be the result of the survival, in 

 the severe struggle for existence, of what is best fitted 

 for the purpose to which it is to be applied. This may 

 or may not be the explanation, but the interest of the 

 study of such an animal as the horse will be increased 

 tenfold by the conviction that there is some true and 

 probably discoverable causation for all its modifications 

 of structure, however far we may yet be from the true 

 solution of the methods by which they have been 

 brought about. 



B 2 



