ANATOMY OF BATRACHIANS. 469 



toads and frogs are 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 ; ft, 

 intestine coiled on itself ; c, liver ; 

 cl, hepatic duct ; e, pancreas ; /, 

 rudimentary hind legs ; g, rectum. 

 After Gervais and Van Beneden. 



a partition in the ventricle. Fig. 

 432 represents the circulatory or- 

 gans of a tadpole, after the gills 



have become absorbed, and before ^Tu^lY'i^t ^udcfe'UVen- 

 the aortic arches are reduced in tricle ; 6 < arterial bulb ; 7, branchial 



artery and its internal branches ; 8, 



number. branchial veins ; 9, aorta ; 10, pul- 



mi _ . , monary artery and its subdivisions- 



The nerVOUS System IS much in the lungs. After Gervais and Van 

 JIT ii.i.n i-ii_ Beneden. 



as in fishes; but the optic lobes 



are rather small; the cerebrum is small.* 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 

 * See Wyman, on the Nervous System of Rana pipiens. Smiths* 

 Contr. 1853. 



