262 THE PRINCIPLES OF [Part IL 



ture, but the breeders in England successfully put one 

 male to four or five females ; nevertheless the first female, 

 as Mr. Fox has been assured, is alone treated as the wife, 

 she and her young ones being fed by him ; the others are 

 treated as concubines. I have noticed these cases, as it 

 renders it in some degree probable that monogamous spe- 

 cies, in a state of nature, might readily become either tem- 

 porarily or permanently polygamous. 



With respect to reptiles and fishes, too little is known 

 of their habits to enable us to speak of their marriage- 

 arrangements. The stickle-back (Gasterosteus), however, 

 is said to be a polygamist ; 10 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 vigorous offspring will be reared from 

 the pairing of the strongest and best-armed males, which 

 have conquered other males, with the most vigorous and 

 best-nourished females, which are the first to breed in the 

 spring. Such females, if they select the more attractive, 

 and at the same time vigorous, males, 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 fe- 

 males ; and this will especially hold good if the male de- 

 fends the female, and aids in providing food for the young. 

 The advantage thus gained by the more vigorous pairs in 

 rearing a larger number of offspring has apparently suf- 

 ficed to render sexual selection efficient. But a large pre- 

 ponderance in number of the males over the females would 



Poultry,' 1848, p. 76) about the eggs of the guinea-fowl being infertile 

 when more than one female is kept with the same male. 

 10 Noel Humphreys, ' River Gardens,' 1857. 



