710 



EVOLUTION OF ANIMALS 



fiUPTURE A/>£A 



Part V 



■BLOOD i^sssns 



CAvirr OF 



OVARY 



INNER 

 MEMBRANE OF. 

 OVARy 



crsT yyALL 



FOLLICLE CELLS 



VITELLINE 

 MEMBRANE 



OUTER 

 OVARIAN WALL 



PERI TONEUM 



RUPTURED 

 FOLLICLE 



EGC EMERGING 

 FROM FOLLICLE 



FOLLICLE CELLS REMAINING WITHIN 



POSTOVULATORf FOLLICLE 

 'SMOOTH MUSCLE OF CrST WALL 



Fig. 34.24. Diagrammatic section through a lobe of the frog's ovary. 1,2,3, 4, 

 and 5 represent stages in the growth of an ovarian follicle (ovum and sac); 6, 

 the break of the peritoneum, the ovarian wall and the follicular sac; 7, the 

 emergence of the egg from the ruptured follicle; 8, the follicle after ovulation. 

 (Courtesy, Turner: General Endocrinology, ed. 2. Philadelphia, W. B. Saunders 

 Co., 1948.) 



The peritoneal lining, the outer surface of the ovary, the liver, and the funnels 

 themselves all bear cilia, each of which waves its microscopic lash toward the 

 destination of the eggs in the oviducts. Motion pictures of the funnel region 

 in anesthetized frogs show the eggs carried inevitably as on a moving stair, 

 coming to the funnels of the oviducts and toppling into them. The eggs are 

 pushed through the oviducts by the contraction of their walls. At the same 

 time, each one is covered with crystalline jelly, just as hens' eggs are coated 

 with the "white" or albumen. They gradually collect in the expanded part of 

 each oviduct, the uterus. Eventually the whole mass from each uterus is ex- 

 pelled at one time, usually while mating. The size and numbers of eggs vary 

 with the species. In the family Ranidae to which leopard frogs belong, there is 

 a range from about 350 eggs in certain species to 20,000 in the bullfrog. The 

 size of the frog does not determine the size of the egg. 



Male Organs. The testes are two relatively small bean-shaped bodies (Fig. 

 34.23). Like all organs in the body cavity their outer covering is continuous 

 with the peritoneal lining. Its extension out over each testis forms a mesentery 

 (mesorchium) by which it is attached to the dorsal wall. Each testis is a com- 

 pact bundle of microscopic, coiled seminiferous tubules. The spermatozoa 

 develop from cells in their linings, when mature, a sum total of many millions. 

 They pass out of the testes through threadlike tubes, the vasa efferentia that 

 extend into the collecting tubes of the kidney which in turn join the ureter. 

 They finally lodge in an expanded part of the ureter (seminal vesicle) where a 

 great number of them accumulate for some time before mating. 



