SEXUAL SELECTION 807 



variations, througli the accumulation of which the male 

 acquired his proper masculine characters, must have oc- 

 curred at a somewhat late period of life; otherwise the 

 young males would have been similarly characterized; 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 ac- 

 quired their present characters probably occurred, accord- 

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

 doubt, for characters are sometimes transferred to the off- 

 spring at an earlier age than that at which they first ap- 

 peared in the parents, so that the parents may have varied 

 when adult, and have transferred their characters to their 

 oilspring while 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; neverthe- 

 less, 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 

 variations 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 obvi- 

 ously 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. 



