428 



MANUAL OF ZOOLOGY 



SECT. 



The ovaries (Fig. 257, Ov) are large folded sacs, on the 

 surface of which the black and white ova project. A fat- 

 body is attached to each. The oviducts (Od} are greatly 

 convoluted tubes, the narrow anterior ends of which open 



CvAo 



FK 



into the ccelom by small 

 apertures ( Of) placed close 

 to the bases of the lungs. 

 Their posterior ends are 

 wide and thin- walled (//), 

 and open into the cloaca 

 (P) . The ova break loose 

 from the surface of the 

 ovary and enter the cce- 

 lomic apertures of the ovi- 

 ducts, the walls of which 

 are glandular, and secrete 

 an albuminous fluid having 

 the property of swelling up 

 in water. The eggs receive 

 a coating of this substance 

 as they pass down the ovi- 

 ducts, and are finally stored 

 up in the thin-walled pos- 

 terior portions of those 

 FIG. 256. Rana esculenta. Urmogenital r 



organs of the male. Ao, dorsal aorta; tubes, which in the 



Cl, cloaca; Cv, post-caval vein ; FK, fat . 



bodies; HO, testes; N, kidneys; S, mg SCaSOn become 



apertures of ureters into cloaca; Ur, .. . 



ureters. (From Wiedersheim's Com- mensely dilated and 



parative Anatomy.) . .. 



as uteri. The eggs are laid 



in water in large masses ; each has one black and one white 

 hemisphere, the former always directed upwards, and is sur- 

 rounded by a sphere of jelly. During oviposition the male 

 sheds his spermatic fluid over the eggs, and the sperms 

 making their way through the jelly impregnate them. 



