510 THE DESCENT OF MAN. 



If all the successive variations were transmitted equally 

 to both sexes the females would be indistinguishable from 

 the males ; and this likewise occurs with many birds. 

 If, however, dull colors were of high importance for the 

 safety of the female during incubation, as with many 

 ground birds, the females which varied in brightness 

 or which received through inheritance from the males 

 any marked accession of brightness would sooner or later 

 be destroyed. But the tendency in the males to continue 

 for an indefinite period transmitting to their female off- 

 spring their own brightness, would have to be eliminated 

 by a change in the form of inheritance; and this, as shown 

 by our previous illustration, would be extremely difficult. 

 The more probable result of the long-continued destruc- 

 tion of the more brightly colored females, supposing tlie 

 equal form of transmission to prevail, would be the lessen- 

 ing or annihilation of the bright colors of the males, 

 owing to their continual crossing with the duller females. 

 It would be tedious to follow out all the other possible 

 results; but I may remind the reader that if sexually lim- 

 ited variations in brightness occurred in the females, even 

 if they were not in the least injurious to them and conse- 

 quently were not eliminated, yet they would not be favored 

 or selected, for the male usually accepts any female, and 

 does not select the more attractive individuals ; conse- 

 quently these variations would be liable to be lost, and 

 would have little influence on the character of the race; and 

 this will aid in accounting for the females being commonly 

 duller-colored than the males. 



In the eighth chapter instances were given, to which 

 many might here be added, of variations occurring at vari- 

 ous ages and inherited at the corresponding age. It was 

 also shown that variations which occur late in life are com- 

 monly transmitted to the same sex in which they first 

 appear; while variations occurring early in life are apt to 

 be transmitted to both sexes; not that all the cases of sexu- 

 ally limited transmission can thus be accounted for. It 

 was further shown that if a male bird varied by becoming 

 brighter while young, such variations would be of no ser- 

 vice until the age for reproduction had arrived, and there 

 was competition between rival males. But in the case of 

 birds living on the ground and commonly in need of the 

 protection of dull colors^ bright tints would be far more 



