XIII 



PHYLUM CHORDATA 



267 



-.- -Ot 



of delicate vasa efferentia which enter the kidney and become con- 

 nected with the urinary tubules. The spermatic fluid is thus 

 passed into the urinary tubules arid carried off by the ureter, which 

 is therefore a urinogenitalduct in the male Frog. A vesicula seminalis 

 (Fig. 876, 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. 884, 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 an- 

 terior ends of which 

 open into the ccelome 

 by small apertures (Ot.) 

 placed close to the bases 

 of the lungs. Their pos- 

 terior 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 pro- 

 perty of swelling up in 

 water. The eggs receive 

 a coating of this sub- 

 stance as they pass down 

 the oviducts and are 

 finally stored up in the 

 thin-walled posterior por- 

 tions of those tubes, which, 

 in the breeding season, 

 become immensely dil- 

 ated and serve as uteri. 



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

 each has one black and one white hemisphere, the former always 

 directed upwards, and is surrounded by a sphere of jelly. The 

 egg is telolecithal, the protoplasm being mainly accumulated on 

 the pigmented hemisphere, while the white hemisphere is loaded 

 with yolk. During oviposition the male sheds his spermatic fluid 



FIG. 884. Rana esculenta. Urinogenital organs o{ 

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

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

 cloacal aperture of oviduct ; S, S', cloacal apertures 

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

 Wiedersheim's Comparative Anatomy.) 



