AJSfATOMY OF BATHACUIANS. 



469 



toads iiud frogs 



lire so highly developed. The trachea is 

 short. 



The heart has two auricles, the right one the larger, and a 

 single ventricle ; but in Proteus the auricles connect with 

 each other, and in the salamanders there is a hole in the par- 

 tition separating the auricles. There are also indications of 



Fig. 431. — Mouth and digestive 

 canal of a Tadpole. A, mouth ; 6, 

 intestine coiled on itself ; c, liver ; 

 rf, hepatic duct ; e, pancreas ; /, 

 rudimentary hind legs ; g, rectum. 

 — After Gervais and Van Beneden. 



a partition in the ventricle. Fig. 

 433 represents the circulatory or- 

 gans of a tadpole, after the gills 

 have become absorbed, and before 

 the aortic arches are reduced in 

 number. 



The nervous system is much 

 as in fishes ; but the optic lobes 

 are rather smaller, as the eyes are smaller. The kidneys are 

 in many respects like those of fishes, especially sharks, as 

 is the internal reproductive system. The ovaries are greatly 

 enlarged during the breeding season. The sperm is usually 

 passed to the kidney, and thence through the ureters out of 

 the cloaca. The oviducts and ureters have a common outlet 



Fig. 433.— Tadpole of a Frog. 1, 

 vena cava ; 2, left auricle ; 3, pul- 

 monary vein and its origin in the 

 two lungs ; 4, left auricle ; 5, ven- 

 tricle ; tl, arterial bulb ; 7, branchial 

 artery and its internal branches; 8, 

 branchial veins ; 9, aorta ; 10, pul- 

 monary artery and its subdivisions 

 in the lungs.— After Gervais and Van 

 Beneden. 



