182 THE REPRODUCTIVE SYSTEM. 



tance at the end) with a protoplasmic sheath. The tail ex- 

 hibits rapid vibratory movements, by means of which the 

 spermatozoon is propelled forward. 



Spermatozoa are real cells, though of unusual type. The 

 head is of the nature of a nucleus, while the tail and a pos- 

 sible protoplasmic envelope about the head may be taken to 

 be cytoplasm. The chromosomes are " reduced." A very 

 minute round body detected by some observers just posterior 

 to the head is perhaps a centrosome. 



FEMALE GENITAL ORGANS. 



The female genital organs are the ovaries, oviducts, uterus, 

 vagina, vulva, vestiges of foetal structures, and mammary 

 glands. The pelvic organs are developed from the embryonic 

 Wolffian body and duct of Miiller and their epithelium is of 

 mesoblastic origin. 



The Ovary. 



The ovary (Fig. 71) consists of a connective-tissue mass or 

 stroma, in which are imbedded large numbers of developing 



FIG. 71. 



Section of ovary of cat (Schron). 1, epithelial covering; 1', hilnm; 2, medulla; 

 8, stroma of cortex ; 4, bloodvessels ; 5, undeveloped ovisacs : 6, 7, 8, developing 

 Graafian follicles; 9, mature Graafian follicles; 10, corpus luteum. 



ova, each in a structure called an ovisac or Graafian follicle ; 

 the whole organ being covered by an epithelial investment. 



