XIII.] THE FROG. 151 



the vomers ; the intestine becomes less and less coiled as, noi 

 growing at the same rate as the body, it becomes relatively 

 shorter; and the animal gradually changes its diet fron 

 vegetable to animal matters — the perfect Frog being insecti 

 vorous. 



The two species, Rana temporaria and Bana esculenta, an 

 distinguishable by the following external characters. Ii 

 Rana temporaria, the interspace between the eyes is flat o: 

 slightly convex, and its breadth is usually greater than, o; 

 at least equal to, that of one of the upper eyelids. Th( 

 diameter of the tympanic membrane is less than that of th( 

 eye, often much less. The horny elevation on the outer sid( 

 of the pes is small or absent, and that on the inner ii 

 flattened and has a rounded margin. A patch of darl 

 colour extends from the eye backwards over the tympanii 

 membrane. The males have the cushion on the radial sid( 

 of the manus black, and they are devoid of vocal sacs. 



In Rana esculenta, on the other hand, the interspace be 

 tween the eyes is usually concave and narrower than th( 

 breadth of one oi the eyelids. The diameter of the tym 

 panic membranKis as great as that of the eye. The horn^ 

 elevation on the inner side of the pes is elongated, com- 

 pressed and brought to a blunt edge, so as almost to resemble 

 a spur, and a small outer elevation is constantly present 

 There is no patch of colour at4he sides of the head, sue! 

 as exists in Rana temporaria, and the cushion of the innei 

 .digit in the male is not black. The males have a larg« 

 pouch on each side of the head, behind the angle of the jaw 

 communicating with the cavity of the mouth, and, wher 

 ■ they croak, these pouches becoming dilated assume the form 

 of spherical sacs. 



Havino' thus become acquainted with the general charactei 

 and life-history of the Frog, and with those features of its 



