Chap. VIII. SEXUAL SELECTION. 263 



the males, but likewise to their various ornaments or 

 other attractions. 



In the converse and much rarer case of the males 

 selecting particular females, it is plain that those which 

 were the most vigorous and had conquered others, would 

 have the freest choice ; and it is almost certain that they 

 would select vigorous as well as attractive females. Such 

 pairs would have an advantage in rearing offspring, more 

 especially if the male had the power to defend the 

 female during the pairing-season, as occurs with some 

 of the higher animals, or aided in providing for the 

 young. The same principles would apply if both sexes 

 mutually preferred and selected certain individuals of 

 the opposite sex ; supposing that they selected not only 

 the more attractive, but likewise the more vigorous 

 individuals. 



Numerical Proportion of the Two Sexes. — I have 

 remarked that sexual selection would be a simple 

 affair if the males considerably exceeded in number 

 the females. Hence I w 7 as led to investigate, as far 

 as I could, the proportions between the two sexes of 

 as many animals as possible ; but the materials are 

 scanty. I will here give only a brief abstract of the 

 results, retaining the details for a supplementary dis- 

 cussion, so as not to interfere with the course of my 

 argument. Domesticated animals alone afford the 

 opportunity of ascertaining the proportional numbers 

 at birth ; but no records have been specially kept for 

 this purpose. By indirect means, however, I have 

 collected a considerable body of statistical data, from 

 which it appears that with most^ of our domestic 

 animals the sexes are nearly equal at birth. Thus with 

 race-horses, 25,560 births have been recorded during 

 twenty-one years, and the male births have been to the 

 female births as 99*7 to 100. With greyhounds the 



