hai\ VIII. Sexual Selection. 233 



amphibians, and fishes ; also with many crustaceans, spiders, and 

 some few insects, such as certain orthoptera and libellulas. In 

 all these cases the variations, through the accumulation of which 

 the male acquired his proper masculine characters, must have 

 occurred at a somewhat late period of life ; otherwise the young 

 males would have been similarly characterised ; and conformably 

 with our rule, the variations are transmitted to and developed in 

 the adult males alone. When, on the other hand, the adult male 

 closely resembles the young of both sexes (these, with rare 

 exceptions, being alike), he generally resembles the adult female ; 

 and in most of these cases the variations through which the young 

 and old acquired their present characters, probably occurred, 

 according to our rule, during youth. But there is here room for 

 doubt, for characters are sometimes transferred to the offspring 

 at an earlier age than that at which they first appeared in the 

 parents, so that the parents may have varied when adult, and 

 have transferred their characters to their offspring whilst young. 

 There are, moreover, many animals, in which the two sexes closely 

 resemble each other, and yet both differ from their young ; and 

 here the characters of the adults must have been acquired late in 

 life ; nevertheless, these characters, in apparent contradiction to 

 our rule, are transferred to both sexes. We must not, however, 

 overlook the possibility or even probability of successive varia- 

 tions of the same nature occurring, under exposure to similar 

 conditions, simultaneously in both sexes at a rather late period 

 of life ; and in this case the variations would be transferred to 

 the offspring of both sexes at a corresponding late age ; and there 

 would then be no real contradiction to the rule that variations 

 occurring late in life are transferred exclusively to the sex in 

 which they first appeared. This latter rule seems to hold true 

 more generally than the second one, namely, that variations 

 which occur in either sex early in life tend to be transferred to 

 both sexes. As it was obviously impossible even to estimate in 

 how large a number of cases throughout the animal kingdom 

 these two propositions held good, it occurred to me to investigate 

 some striking or crucial instances, and to rely on the result. 



An excellent case for investigation is afforded 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 

 reindeer, on the other hand, the female is provided with horns ; 

 so that in this species, the horns ought, according 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 



