REPRODUCTION 19 



21. Primary and secondary sexual characters. - 



The particular characteristics which differentiate the 

 male from the female sex may be divided into primary 

 and secondary characters. The primary characters are 

 those which are peculiar to the sex. In the male, the 

 form and functions of the generative organs clearly 

 differentiate him from the female. As Lee l has pointed 

 out, the function of the primary sexual characters of 

 the male is the production of spermatozoa and the im- 

 pregnation of the female egg. The activities of the 

 primary sexual organs of the female center about the 

 production of the egg and the development of the 

 embryo. 



The secondary sexual characters are those which may 

 often be possessed in common by both sexes but experi- 

 ence a special and somewhat different development in 

 the two sexes. Examples of secondary sexual characters 

 are the horns of the ram in some breeds of sheep, the 

 spurs of the cock, the tusks of the boar, the various col- 

 ored plumage of many male birds, and the crest in stal- 

 lions and bulls. Under certain conditions, the secondary 

 sexual characters which are in general characteristic of 

 the male sex alone may be developed in the female. Thus, 

 hens sometimes develop spurs and ewes develop horns. 



Castration of the male causes a check in the develop- 

 ment of the secondary sexual characters and causes the 

 male to approach more nearly to the form and appear- 

 ance of the female. 



22. The reproductive organs of the male (Fig. 5). The 

 organs of generation in the male are : (a) the testicles, cor- 

 responding to the ovaries in the female ; (b) vasa deferentia, 

 or the ducts leading from the testicles to the ejaculatory 



1 "American Text Book of Physiology," 1903, p. 443. 



