THE SEXES AND SEXUAL SELECTION. I3 



SUMMARY. 



I., II. — The existence of male and female animals is a commonplace of 

 observation. They differ in primary and in secondary sexual characters, of 

 which illustrations are given, chiefly from Darwin. 



III. — Darwin's hypothesis of sexual selection assumes the preservation and 

 perfection of variations, advantageous in courtship or in battles with rivals. 



IV. — Wallace maintains that the females have been protectively retarded 

 by natural selection; Brooks, that the males predominate in power of trans- 

 mitting variations, and are therefore more divergent; while Mivart demands a 

 deeper analysis than is afforded by either sexual or natural selection, — such 

 a physiological rationale being hinted at. 



LITERATURE. 



Brooks, W. K. — The Law of Heredity: A Study of the Cause of Variation and 



the Origin of Living Organisms. Baltimore, 1883. 

 Darwin, C. — On the Origin of Species by Means of Natural Selection; or, 



The Preservation of Favored Races in the Struggle for Life. [No. 58 and 



No. 59 of The Humboldt Library] 

 - The Descent of Man, and Selection in Relation to Sex. [Nos. 74, 75, 76, 



77 of The Humboldt Library] 

 Mivart, St. George. — Lessons from Nature. London, 1876. 

 Wallace, A. R. — Contributions to the Theory of Natural Selection. London, 



1871. 

 Darwinism: An Exposition of the Theory of Natural Selection, with 



Some of its Applications. [No. 115 and No. 1 16 of The Humboldt Library] 



