THE BATRACHIA OF NORTH AMERICA. ll 



arise parallel to the cardinal veins, and empty into the anterior cardi- 

 nals on each side, in front of the Ductus cuvierl. These are the verte- 

 bral veins. The portion of the posterior cardinals between the Ductus 

 cuvieri and the kidney disappears, so that what remains of the pos- 

 terior cardinals are only renales advehentes. The anterior cardinals 

 become the jugulars. The principal posterior vein is the vena cava pos- 

 terior, which is median, and consists originally of the renales revehentes 

 from the kidney. It receives the hepatic vein before emptying into the 

 sin us venosus. The iliac veins pass directly into the kidney after re- 

 ceiving the V. caudaUs. 



The lymph cavities of the body in the Batrachia are extensive. This 

 is especially the case with the Salientia, where the skin is loosely at- 

 tached, and incloses large spaces immediately below it. The lymphatic 

 vessels from the digestive system open into these cavities. The ves- 

 sels also empty into the veins, and present at such jjoints enlargements 

 which contract rhythmically, and are known as " lymph-hearts." They 

 are situated in the sacral region, one on each side, in the tailed forms, 

 while an additional pair is present in the scapular region in the Sali- 

 entia. 



The reproductive and urinary systems are closely connected in the 

 Batrachia, and must be treated of together. Both discharge their con- 

 tents into the alimentary canal, forming a cloaca, Their structure is 

 best understood by reference to that of the sharks. In these fishes a 

 primitive longitudinal vessel on each side of the dorsum of the abdom- 

 inal cavity sends branches to the outer side, which there form convo- 

 luted lobules, the primitive kidney. In the Batrachia this longitudinal 

 or archinephric duct divides longitudinally, and the inner portion re- 

 mains as the Miillerian duct. This becomes the oviduct of the. female. 

 The external half with its series of branches becomes the urogenital 

 duct. The testes and ovaries are developed independently external to 

 the kidneys, and the former send their efferent ducts directly into the 

 latter. The ovaries discharge the eggs into the abdominal cavity, 

 whence they pass into the oviducts by the free open extremities of the 

 latter, and are thence ejected by the anus, after receiving a covering 

 of albumen. The male organ homologous with the Miillerian duct is 

 of reduced size in all the Salientia except the Ean^e and allies, where it 

 is aborted. It has been shown, however, to persist in our Bana virens. 

 In the Urodela the vasa deferentia pass through the kidney and enter 

 the genitoiirinary duct, and so into the cloaca ; but in the Salientia the 

 efferent ducts of the kidney collect themselves into a separate tube or 

 ureter, which, however, joins the single vas deferens before entering 

 the cloaca. But the Discoglossidae agree with the Urodela in this, as 

 in several other respects. A urinary bladder is always present in the 

 Batrachia. The testes are single on each side in the Salientia ; there 

 are several in the Urodela, especially in the Cseciliidpe. The penis is 

 wanting. Impregnation is accomplished by copulation in the Urodela, 



