ELEPHANTS, RHINOCEROSES, AND HORSES 263 



these huge incisors have a band of enamel over the lower 

 portions; but this enamel has almost entirely disappeared in 

 the tusks of modern elephants, being reduced to a small patch 

 at the top, which is soon worn away in the young animal. These 

 incisor teeth begin with a pair of "milk" tusks, which fall out 

 when the young elephant is a few years old, and are replaced by 

 permanent teeth in the ordinary way. 



Modern elephants are to a great extent devoid of hair in 



PATTERN OF ENAMEL AND DENTINE ON SURFACE OF MOLAR OF AFRICAN ELEPHANT. 



PATTERN OF ENAMEL AND DENTINE ON SURFACE OF MOLAR OF INDIAN ELEPHANT. 



the adult, except for the fringe of thick bristles at the end of the 

 tail ; but the present writer and others have been able to testify- 

 that the newly-born African and Indian elephants are fairly well 

 covered with hair are quite hairy animals, in fact. In the 

 African elephant this early hair is black. In extinct elephants, 

 such as the mammoth, which grew accustomed to live in cold 

 climates, the hair developed to an extravagant extent. Excessive 

 development of any organ or feature often runs parallel with 

 complete disappearance. Thus, in the human being as 



in 



