Chap. XXI.] AND CONCLUDING REMARKS. 381 



for a long time choosing the most pleasing or useful indi- 

 viduals, without any wish to modify the breed. 



The laws of inheritance determine whether characters 

 gained through sexual selection by either sex shall be 

 transmitted to the same sex, or to both sexes; as well as 

 the age at which they shall be developed. It appears 

 that variations which arise late in life are commonly trans- 

 mitted to one and the same sex. Variability is the neces- 

 sary basis for the action of selection, and is wholly inde- 

 pendent of it. It follows from this, that variations of the 

 same general nature have often been taken advantage of 

 and accumulated through sexual selection in relation to 

 the propagation of the species, and through natural selec- 

 tion in relation to the general purposes of life. Hence 

 secondary sexual characters, when equally transmitted to 

 both sexes, can be distinguished from ordinary specific 

 characters only by the light of analogy. The modifica- 

 tions acquired through sexual selection are often so 

 strongly pronounced that the two sexes have frequently 

 been ranked as distinct species, or even as distinct genera. 

 Such strongly-marked differences must be in some manner 

 highly important; and we know that they have been 

 acquired in some instances at the cost not only of incon- 

 venience, but of exposure to actual danger. 



The belief in the power of sexual selection rests chiefly 

 on the following considerations : The characters which 

 we have the best reason for supposing to have been thus 

 acquired are confined to one sex ; and this alone renders 

 it probable that they are in some way connected with the 

 act of reproduction. These characters in innumerable in- 

 stances are fully developed only at maturity ; and often 

 during only a part of the year, which is always the breed- 

 ing-season. The males (passing over a few exceptional 

 cases) are the most active in courtship ; they are the best 

 armed, and are rendered the most attractive in i^arious 



