XIII 



PHYLUM CHORD ATA 



287 



CvAo 



FK 



from the outer borders of the kidneys and open into the dorsal 

 wall of the cloaca (CL). The kidney is developed from the 

 mesonephros of the embryo, the ureter from the mesonephric duct. 

 In the larva a large pronephros is present and is, for a time, the 

 functional kidney. 



Opening into the cloaca on its ventral side is an organ 

 (Fig. 929, U.) mentioned in the general account of the Craniata 

 (p. 120), but here actually met with for the first time. It is a 

 bilobed, thin-walled, and very delicate sac into which the 

 urine passes by gravitation from the cloaca when the anus is 

 closed. The sac is a urinary 

 bladder, but, as it is quite different 

 morphologically from the organ of 

 the same name in Fishes, which is 

 a dilatation of the ureter, it is dis- 

 tinguished as the aUantoic Madder. 



The testes (HO) are white ovoid 

 bodies lying immediately ventral 

 to the anterior ends of the kid- 

 neys, to which they are attached 

 by folds of peritoneum. From 

 the inner edge of each pass a 

 number of delicate vas effercntia 

 which enter the kidney and be- 

 come connected with the urinary 

 tubules. The spermatic fluid is 

 thus passed into the urinary 

 tubules and carried off by the 

 ureter, which is therefore a urino- 

 genital duct in the male Frog. A 

 vesicula seminalis (Fig. 929, vs. sera.) 

 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 waries (Fig. 938, 00.) 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 into the ccelome by small 

 apertures (0.) 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 ccelomic 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 



FIG. 937. Rana esculenta. Urino- 

 genital organs of the male. Ao. dorsal 

 aorta ; Cl. cloaca ; Cv. postcaval vein ; 

 FK, fat bodies ; HO, testes ; N, kidneys ; 

 S, apertures of ureters into cloaca ; Ur. 

 ureters. (From Wiedersheim's Com- 

 parative Anatomy.) 



