26 



THE DIRECTION OF HAIR ON THE BODIES 

 OF ANIMALS. 



PAPER READ BY 



WALTER KIDD, Esq., M.D., F.Z.S., 



On January 23rd, 1901. 



It is not so simple a matter as it would appear at first 

 sight to find out why the hairy covering of animals takes the 

 directions which it is found to take. Broadly speaking this 

 direction is from the cephalic to the caudal extremity of the 

 body, and from the proximal to the distal extremities of the 

 limbs. To this general distribution there are a variety of 

 exceptions, and I think not only that the rule but the excep- 

 tions are of considerable interest, and perhaps of importance. 

 The aetilogy of this point might be settled straight off by 

 the crude statement that adaptation to their surroundings 

 requires that the hairy covering of wild animals should set 

 in certain directions, and that the ordinary one referred to is 

 the best adapted. This is like many of the biological 

 questions in which the somewhat magic word " adaptation " 

 is uttered to cover up want of knowledge. 



I would submit that there are only two feasible explana- 

 tions, according to biological methods, of these general and 

 particular facts, the rule and the exceptions. They are : — 

 First, that the directions of hair found are of advantage to 

 the possessor in the struggle for existence, and so they would 

 come under the jurisdiction of natural selection. Secondly, 

 that they are determined by the habits and environments of 

 the animals in question. Broadly speaking, we must choose 

 between these two, and I will refer to these again after the 

 facts of the case have been more fully stated, and to certain 

 views which others have held. 



