XIII 



PHYLUM CHORDATA 



279 



passes by gravitation from tlie cloaca when the anus is closed. 

 The sac is a urinary bladder, but, as it is quite different morpho- 

 logically from the organ of the same name in Fishes, which is a 

 dilatation of the ureter, it is distinguished as the allantoic bladder. 



The testes (HO) are white ovoid bodies lying immediately ventral 

 to the anterior ends of the kidneys, to which they are attached by 

 folds of peritoneum. From the inner edge of each pass a number 

 of delicate vas efferentia 

 which enter the kidney and 

 become connected with the 

 urinary tubules. The sper- 

 matic fluid is thus passed 

 into the urinary tubules 



and carried off by the Q^ 



ureter, which is therefore 

 a urinogenital duct in the 

 male Frog. A vesicula semi- 

 nalis (Fig. 940, vs. sem.) 

 opens by numerous small 

 ducts into the outer side 

 of the ureter. Attached 

 to the testis are lobed 

 bodies of a bright yellow 

 colour, the fat-bodies (FK). 



The ovaries (Fig. 949, 

 Ov.) are large folded sacs 

 on the surface of which the 

 black-and-white ova pro- 

 ject. A fat-body is attached 

 to each. The oviducts (Od.) 

 are greatly convoluted 

 tubes, the narrow anterior 

 ends of which open into 

 the coslome by small aper- 

 tures (Ot.) placed close to 

 the bases of the lungs. 

 Their posterior ends are 

 wide and thin- walled (Ut.), 

 and open into the cloaca 

 (P). The ova break loose from the surface of the ovary and enter 

 the coelomic apertures of the oviducts, 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 oviducts and are finally stored up in the 

 thin-walled posterior portions of those tubes, which, in the breed- 

 ing season, become immensely dilated and serve as uteri. 



Development. The eggs are laid in water in large masses ; 



s 2 



m 



FIQ. 949. Rana esculcnta. Urinogeuital organs of 

 the female. N, kidneys ; Od. oviduct ; Ot, its coelomic 

 aperture ; Ov. left ovary (the right is removed) ; P, 

 cloacal aperture of oviduct ; S, S' t cloacal apertures 

 of ureters ; Ut, uterine dilatation of oviduct. (From 

 Wiedersheim's Comparative Anatomy.) 



