764 



A TEXTBOOK OF PHYSIOLOGY 



The Reproductive Processes in the Male. The sexual apparatus in 

 the male consists of (1) the testis, in which the spermatozoa are 



E 



FIG. 470. DIAGRAMS SHOWING THE ESSENTIAL FACTS IN THE MATURATION OF THE 

 OVUM. THE SOMATIC NUMBER OF CHROMOSOMES is SUPPOSED TO BE FOUR. 

 (Redrawn from Wilson's "The Cell," etc.) 



A, Initial phase: two tetrads have been formed in the germinal vesicle; B, two 

 tetrads have been drawn up about them to form the equatorial plate of the first 

 mitotic figure; C, the mitotic figure has rotated into position, leaving the remains 

 of the germinal vesicle at gv; D, formation of first polar body (pb l ) : each tetrad 

 divides into two dyads; E, first polar body formed, two dyads in it and in the 

 egg; F, preparation for the second division; G, second polar body (pi 2 ) forming 

 and the first dividing: each dyad divides into two single chromosomes; H, final 

 result: three polar bodies and" the egg nucleus ( $ ), each containing two single 

 chromosomes (half the somatic number); c, the egg-centrosome, which now 

 degenerates and is lost. 



produced; (2) in higher animals, accessory sexual glands (the prostate, 

 vesiculse seminales, and glands of Cowper), which aid in the formation 



