300 THE PEINCIPLES OF Part II. 



and shall endeavour in each case to apply tbe prin- 

 ciples 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 structures 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 members of the two sexes 

 in animals belonging to various classes. 



As no one, as far as I can discover, has paid atten- 

 tion to the relative numbers of the two sexes through- 

 out the animal kingdom, I will here give such materials 

 as I have been able to collect, although they are ex- 

 tremely imperfect. They consist in only a few instances 

 of actual enumeration, 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. 



Man. — In England during ten years (from 1857 to 

 1866) 707,120 children on an annual average have 

 been born alive, in the proportion of 104*5 males to 

 100 females. But in 1857 the male births through- 

 out England were as 105*2, and in 1865 as 104*0 to 

 100. Looking to separate districts, in Buckinghamshire 

 (where on an average 5000 children are annually born) 



