242 The Descent of Man. Part IL 



transmitted to one sex alone ; and such, variations, thus preserved 

 and transmitted, have given rise to secondary sexual characters. 

 In the following chapters, I shall treat of the secondary- 

 sexual characters in animals of all classes, and shall endeavour 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 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 the aid of which the male 

 conquers other males, and by which he allures or excites the 

 female, wull 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 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 only 

 in mankind, I w T ill first give them as a standard of comparison. 



Man. — In England during ten years (from 1857 to 1866) the 

 average number of children born alive yearly was 707,120, in 

 the proportion of 104*5 males to 100 females. But in 1857 the 

 male births throughout England were as 105*2, and in 1865 as 

 104*0 to 100. Looking to separate districts, in Buckingham- 

 shire (where about 5000 children are annually born) the mean 

 proportion of male to female births, during the whole period of 

 the above ten years, was as 102*8 to 100 ; whilst in N. Wales 

 (where the average annual births are 12,873) it was as high 

 as 106*2 to 100. Taking a still smaller district, viz., Port- 

 landshire (where the annual births average only 739), in 1864 

 the male births were as 114*6, and in 1862 as only 97*0 to 

 100 ; but even in this small district the average of the 7385 

 births during the whole ten years, was as 104*5 to 100 ; that is in 

 the same ratio as throughout England. 48 The proportions are 

 sometimes slightly disturbed by unknown causes; thus Prof. 



* 18 • Twenty-rinth Annual Report In this report (p. xii.) a special <le« 

 of the Registrar-General for I86f .' connial table is given. 



