REPRODUCTION 



When the ejected sex-cells do not directly encounter 

 each other (as in many aquatic organisms), ^ special 

 structures have to be formed to convey the fertilizing 

 sperm from the male to the female body. This process 

 of copulation becomes important, as it is associated with 

 characteristic feelings of pleasure, which may cause ex- 

 treme psychic excitement; as sexual love it becomes, 

 in man and the higher animals, one of the most powerful 

 springs of vital activity. In many of the higher ani- 

 mals (namely, vertebrates, articulates, and moUusks) 

 there are also formed a number of glands and other 

 auxiliary organs which co-operate in the copulation. 



The manifold and intimate relations which exist, in 

 man and the higher animals (especially vertebrates and 

 articulates), between their sexual life and their higher 

 psychic activity, have given rise to plenty of "wonders 

 of life." Wilhelm Bolsche has so ably described them 

 in his famous and popular work. The Life of Love in 

 Nature, that I need only refer the reader to it. I will 

 only mention the great significance of what are called 

 "secondary sexual characters." These characteristics 

 of one sex that are wanting in the other, and that are 

 not directly connected with the sexual organs — ^such as 

 the man's beard, the woman's breasts, the lioli's mane, 

 or the goat's horns — have also an aesthetic interest; they 

 have, as Darwin showed, been acquired by sexual selec- 

 tion, as weapons of the male in the struggle for the 

 female, and vice versa. The feeling of beauty plays a 

 great part in this, especially in birds and insects; the 

 beautiful colors and forms which we admire in the male 

 bird of paradise, the humming-bird, the pheasant, the 

 butterfly, etc., have been formed by sexual selection 

 (cf. the History of Creation). 



In various groups of the histona the male sex has 

 become superfluous in the course of time; the ovula 

 develop without the need of fertilization. That is par- 



