MATING 63 



sex cells are brought together in a casual manner, by 

 water-currents, etc., sometimes within, sometimes 

 outside the body. When sufficiently near each other, 

 the germ cells are drawn together by a sort of chemical 

 affinity. 



But in the higher animals special precautions are 

 taken for the safe union of the sex cells. The male 

 fish, being attracted to the female, follows her about, 

 and as she lays the eggs he fertilizes them with his 

 sperm. A further step is made in the case of the 

 frog: here the female protrudes her eggs from her 

 body, and the male, embracing her, discharges his 

 sperm on to the eggs as they are laid. 



In the highest organisms, however, nothing is left 

 to chance. Special organs are developed for the 

 purpose of close copulation: these are the external 

 sex organs. In the male, the organ of immission 

 (for conveying the sperm into the female passage) is 

 called the penis. It is essentially a long, soft, finger- 

 shaped appendage with a passage running right along 

 it. This passage is connected by a long tube with the 

 testes. While the ovaries in all higher animals, in- 

 cluding Man, are situated internally within the abdo- 

 men, the testes are external, being contained in a 

 pouch suspended from the pubes. The sperm is 

 formed in the male sex glands or testes. During 

 copulation it passes, mixed with some viscid secre- 

 tion, out by the penis as semen, and is conveyed into 

 the sex passage of the female. It is evident that for 

 this purpose the male organ must enter the female 

 passage. The introduction of the penis into the 

 vagina takes place during the process of copulation. 

 The discharge of semen into the vagina is called the 



