290 THE PRINCIPLES OE [Pari tt 



characters are concerned, would be left unmodified, except- 

 ing in so far as she may have received them by transference 

 from the male. No doubt if the female varied and trans- 

 ferred serviceable characters to her male offspring, these 

 would be favored through sexual selection ; and then both 

 sexes would thus far be modified in the same manner. But 

 I shall hereafter have to recur to these more intricate con- 

 tingencies. 



In the following chapters, I shall treat of the secondary 

 sexual characters in animals of all classes, and shall en- 

 deavor in each case to apply the principles explained in 

 the present chapter. The lowest classes will detain us for 

 a very short time, but the higher animals, especially birds, 

 must be treated at considerable length. It should be borne 

 in mind that, for reasons already assigned, I intend to give 

 only a few illustrative instances of the innumerable struct- 

 ures by the aid of which the male finds the female, or, 

 when found, holds her. On the other hand, all structures 

 and instincts by which the male conquers other males, 

 and by which he allures or excites the female, will be fully 

 discussed, as these are in many ways the most interesting. 



/Supplement on the proportional numbers of the two sexes 

 in animals belonging to various classes. 



As no one, as far as I can discover, has paid attention 

 to the relative numbers of the two sexes throughout the 

 animal kingdom, I will here give such materials as I have 

 been able to collect, although they are extremely imper- 

 fect. They consist in only a few instances of actual enu- 

 meration, and the numbers are not very large. As the 

 proportions are known with certainty on a large scale in 

 the case of man alone, I will first give them, as a standard 

 of comparison. 



