A REPRESENTATIVE VERTEBRATE. FROG 



341 



the vasa efferentia, then to the urinary duct 



by a route that differs in different species. 

 The urinary duct is dilated at the posterior 

 end in some species to form the seminal 



vesicle. The sperms then pass from the uri- 

 nary duct or seminal vesicle, as the case may 

 be, to the outside through the cloacal open- 

 ing. 



Ostium 



Esopha 



Fat body 



Ovary 

 with egg 



Large 

 intestin 



Part of oviduct 

 omitted 



Adrenal gland 

 Renal vein 



Oviduct 



Kidney 



Posterior 

 vena cava 



Urinary duct 



Uterus 



oaca 



oacol opening 



Bladd 



Figure 223. Urogenital system of the female frog in ventral view; left ovary removed. 



The eggs arise in the ovaries of the female 

 (Fig. 223); and during the breeding season, 

 they break through the ovarian walls into the 

 body cavity. There they are moved anteriorly 

 by the beating of cilia which cover the 

 peritoneum. The cilia at the entrance to the 

 oviduct, the ostium, create currents which 

 draw the eggs into the convoluted oviduct; 

 they are carried down the oviduct into the 

 thin-walled distensible uterus by action of 

 the cilia in the oviduct. The glandular wall 

 of the oviduct secretes the gelatinous coats 

 of the eggs. The fertilization and develop- 

 ment of the eggs will be described later. 



Just in front of each reproductive organ 

 is a yellowish, glove-shaped fat body which 

 probably constitutes reserve supplies of food 

 that serve the animal during its period of 

 hibernation. 



Reproductive organs of man 



The reproductive organs of human beings 

 (Fig. 225) resemble those of the frog rather 

 closely. In the male, the two testes produce 

 sperms and internal secretions. Within the 

 testes are seminiferous tubules which unite 

 to form the epididymis, a much coiled tub- 

 ule about 20 feet long. The epididymis leads 

 into the sperm duct (vas deferens); this 

 duct joins the duct of a seminal vesicle to 

 form an ejaculatory duct. The ejaculator}' 

 ducts open into the urethra. Near this point 

 is situated a gland about the size of a chest- 

 nut, the prostate gland. On either side of 

 the gland is a body about the size of a pea, 

 the bulbourethral ( Cowper's ) gland. Sperms 

 are formed in the testes and pass down the 

 vasa deferentia. Secretions are supplied by 



