

SEXUAL SELECTION. 241 



An excellent case for investigation is af- 

 forded by the deer family. In all the species, 

 but one, the horns are developed only in the males, 

 though certainly transmitted through the females, and 

 capable of abnormal development in them. In the rein- 

 deer, on the other hand, the female is provided with 

 horns ; so that, in this species, the horns ought, accord- 

 ing to our rule, to appear early in life, long before the 

 two sexes are mature, and have come to differ much in 

 constitution. In all the other species the horns ought to 

 appear later in life, which would lead to their develop- 

 ment in that sex alone in which they first appeared in 

 the progenitor of the whole family. Now, in seven spe- 

 cies, belonging to distinct sections of the family, and in- 

 habiting different regions, in which the stags alone bear 

 horns, I find that the horns first appear at periods vary- 

 ing from nine months after birth in the roebuck, to ten, 

 twelve, or even more months in the stags of the six other 

 aud larger species. But with the reindeer the case is 

 widely different ; for, as I hear from Professor Nilsson, 

 who kindly made special inquiries for me in Lapland, the 

 horns appear in the young animals within four or five 

 weeks after birth, and at the same time in both sexes. 

 So that here we have a structure developed at a most 

 unusually early age in one species of the family, and like- 

 wise common to both sexes in this one species alone. 



Finally, from what we have now seen of 

 the relation which exists in many natural spe- 

 cies and domesticated races, between the period of the 

 development of their characters and the manner of their 

 transmission — for example, the striking fact of the early 

 growth of the horns in the reindeer, in which both sexes 

 bear horns, in comparison with their much later growth 



