824 Heredity. 



recognized, although no one, so far as I know, has 

 attempted to trace them back to a fundamental law of 

 heredity. On the contrary, most of the authors who have 

 discussed them have treated them rather as special cases 

 than as the results of a general principle, and analysis 

 shows that none of the explanations which have been 

 advanced are sufficiently broad to cover the whole 

 ground. 



Daines Barrington and Wallace have held that the ex- 

 planation of the fact that male birds and male insects are 

 often so much more brilliantly colored and conspicuously 

 ornamented than the females is to be found in the fact 

 that the female, wdiile laying her eggs or while incubat- 

 ing, is much more exposed to the attacks of enemies than 

 the male, and that inasmuch as the perpetuation of the 

 race depends upon the safety of the females at this time, 

 natural selection has gradually exterminated the con- 

 spicuous females, and has preserved those with the least 

 striking colors. 



We know, however, that the male is usually mord 

 brilliantly colored than the female among reptiles which 

 do not incubate, and even among certain fishes where the 

 male attends to the eggs and young. It is therefore clear 

 that Wallace's explanation stops short of the whole truth, 

 and Darwin's exhaustive review of the subject seems to 

 prove that among birds it is the male and not the female 

 which has been directly modified. 



Darwin believes that the greater modification of the 

 males as compared with the females is due to sexual 

 selection. The males have struggled with each other for 

 the possession of the females, or have been selected by 

 the females, and this jirocess long continued is believed 

 by him to have resulted in the perpetuation of the strong- 

 est, best armed, or most attractive males. 



