216 THE DESCENT OP MAN. 



able us to speak of their marriage arrangements. The stickle- 

 back (Gasterosteus), however, is said to be a polygamist;" and 

 the male during the breeding season differs conspicuously from 

 the female. 



To sum up on the means through which, as far as we can judge, 

 sexual selection has led to the development of secondary sexual 

 characters. It has been shown that the largest number of vig- 

 orous offspring will be reared from the pairing of the strongest 

 and best-armed males, victorious in contests over other males, 

 with the most vigorous and best-nourished females, which are 

 the first to breed in the spring. If such females select the more 

 attractive, and at the same time vigorous males, they will rear a 

 larger number of offspring than the retarded females, which must 

 pair with the less vigorous and less attractive males. So it will 

 be if the more vigorous males select the more attractive and at 

 the same time healthy and vigorous females; and this will es- 

 pecially hold good if the male defends the female, and aids In pro- 

 viding food for the young. The advantage thus gained by the 

 more vigorous pairs in rearing a larger number of offspring has 

 apparently sufficed to render sexual selection efficient. But a 

 large numerical preponderance of males over females will be still 

 more efficient; whether the preponderance is only occasional and 

 local, or permanent; whether it occurs at birth, or afterwards 

 from the greater destruction of the females; or whether it in- 

 directly follows from the practice of polygamy. 



The Male generally more modified than the Female. — Through- 

 out the animal kingdom, when the sexes differ in external appear- 

 ance, it is, with rare exceptions, the male which has been the 

 more modified; for, generally, the female retains a closer resem- 

 blance to the young of her own species, and to other adult mem- 

 bers of the same group. The cause of this seems to lie in the 

 males of almost all animals having stronger passions than the fe- 

 males. Hence it is the males that fight together and sedulously 

 display their charms before the females; and the victors transmit 

 their superiority to their male offspring. Why both sexes do not 

 thus accfuire the characters of their fathers, will be considered 

 hereafter. That the males of all mammals eagerly pursue the fe- 

 males is notorious to every one. So it is with birds; but many 

 cock birds do not so much pursue the hen, as display their plum- 

 age, perform strange antics, and pour forth their song in her 

 presence. The male in the few fish observed seems much more 

 eager than the female; and the same is true of alligators, and 

 apparently of Batrachians. Throughout the enormous class of in- 



" Noel Humphreys, 'River Gardens,' 1857. 



