160 GENERAL ZOOLOGY 



The ovaries are a pair of tabulated organs, each of which is 

 attached by a mesovarium to the dorsal body wall just in front 

 of the kidney. The paired oviducts or Mullerian ducts are 

 long convoluted tubes, each of which is provided with an opening 

 or ostium at its narrow anterior end and a widened region or 

 uterus near its posterior end just before it enters the cloaca. 

 Since the ostia of the oviducts are located in the region of the 

 pericardium, near the base of the lungs, they are separated by 

 T ct some distance from the ovaries. When 



\ / /*ZIM3\ ^ ne e *=§ s f° rme d m the ovary are mature, 



/^^^^^^\ they escape into the body cavity through 



I • ' :: ^^m^^~a\ ^ ne ru Pt ure °f the walls of the egg follicles 



IX.V.V.^3^^^^IL^---- K and are carried by ciliary movement over 



\i0^\Mr^}/ the ciliated surface of the liver, body 



|\S37 wall, and pericardium to the ostia where 



WW/ they are engulfed. In the upper parts of 



the oviducts the eggs receive a coating of 



^ -UR thin albumen and then pass into the 



uterus where they are stored until 

 Fig. 106. — Diagram of spawned. Oviducts are developed in 



urogenital organs of male both maleg d f emaleg but m the former 

 frog, left side, bd, Bidder s / 



duct; ct, collecting tubules they become reduced in size and remain 



of kidney, which also receive f urxc tionless (FigS. 17 and 18). 

 unniferous tubules, not i • 



shown; e, vasa efferentia, Fat Body. — At the anterior end of each 



through which sperm from f the gonadg f both gexeg of t h e frog is 

 testis reach Bidders duct; ° , ° 



k, kidney, shown in section the fat body, a conspicuous mass of fatty 

 t, testes; ur, ureter. tissue drawn out into finger-shaped lobes 



(Fig. 18). Its development is closely associated with the develop- 

 ment of the gonad, in consequence of which the fat bodies are 

 thought to represent degenerated segments of the embryonic 

 rudiment from which the gonads develop. In temperate zones 

 spawning takes place in the first warm days of spring that signal- 

 ize the end of hibernation and the resumption of more active life. 

 The fat bodies retain their full size throughout the period of hiber- 

 nation but just before the beginning of the breeding season they 

 undergo a reduction in fat content that continues until spawning 

 is completed. The fat bodies thus serve to meet the energy 

 requirements of the developing germ cells and of the bodily activi- 

 ties of the frog before active feeding is resumed. The fat may be 

 drawn upon to meet metabolic requirements at other times, but 



