The Descent of Man 



is of two kinds; in the one it is between the 

 individuals of the same sex, generally the male-;. 

 in order to drive away or kill their rivals, the 

 females remaining passive; while in the other, 

 the struggle is likewise between the individuals 

 of the same sex, in order to excite or charm 

 those of the opposite sex, generally the females, 

 which no longer remain passive, but select the 

 more agreeable partners. This latter kind of 

 selection is closely analogous to that which 

 man unintentionally, yet effectually, brings to 

 bear on his domesticated productions, when 

 he preserves during a long period the most 

 pleasing or useful individuals, 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; as well as the age at which they 

 shall be developed. It appears that variations 

 arising late in life are commonly transmitted 

 to one and the same sex. Variability is the 

 necessary basis for the action of selection and 

 is wholly independent of it. It follows from 

 this that variations of the same general nature 

 have often been taken advantage of and accumu- 

 lated through sexual selection in relation t<> the 

 propagation of the species, as well as through 

 natural selection in relation to the general pur- 

 poses of life. Hence secondary sexual ehaiv 

 when equally transmitted to both srxes. can 

 be distinguished from ordinary specific characters 

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