ITS NEAREST EXISTING RELATIONS. 69 



same situation in many species of deer and antelopes, 

 which lodges a glandular infolding or pouch of the 

 skin called the "suborbital gland/' "crumen," or in 

 French " larmier/' that there can be little doubt but 

 that it had the same purpose in the hipparion. The 

 gland in the existing animals that possess it secretes 

 a peculiar oily, odorous substance, the scent of which 

 enables the animals provided with it to recognize 

 each other even at immense distances, the faculty of 

 smell being also developed to a wonderful degree. 

 At certain seasons of the year the glands are es- 

 pecially active, and their position is such that when 

 the animal is feeding particles of the odorous secre- 

 tions will fall on and adhere to the herbage around, 

 and thus afford indications to any other animals of 

 the same species that may for some time afterwards 

 pass over the same ground. 



The presence of this gland in the hipparion and 

 its absence in the more modern Equidce has been 

 given as a reason for supposing that the latter are 

 not the direct descendants of the former, but must 

 have been derived from some other form in which 

 such a specialization had not been developed. This, 

 of course, is probable ; but it must not be forgotten 

 that very slight changes in habits, or the increased 

 power and use of other senses than that of smell, 

 may have diminished the value of the information 



