BATRACHIA 



137 



01- 



ClI. 



The brain of the frog (Fig. 259) is much like that of a fish 

 (Fig. 224). The olfactory, cerebral, and optic lobes, cerebellum 

 and medulla are in the same relative position, although their rela- 

 tive sizes are not the same. Compared with the 



other parts, are the 



olfactory lobes more 



or less developed 



than in a fish? The 



cerebral hemispheres ? 



The optic lobes? The 



cerebellum? There is 



a cavity in the brain. 



It is readily exposed 



on the under surface 



of the medulla by cut- 

 ting the membrane, 



which is there its only 



covering (Fig. 259). 



FIG. 259. 

 BRAIN OF FROG. 



FIG. 260. NERVOUS SYSTEM 

 OF FROG. 



Frogs and toads are beneficial (why ? ) and do not the slight- 

 est injury to any interest of man. If toads are encouraged 

 to take up their abode in a garden, they will aid in ridding 

 it of insects. A house may be made in a shady corner with 

 four bricks, or better still, a hole a foot deep may be dug to 

 furnish them protection from 

 the heat of the day. A toad's 

 muzzle is not so tapering as a 

 frog's (why ?), its feet are not 

 so fully webbed (why?), and its 

 skin is not so smooth (why ?). 

 In case of doubt open the mouth 

 and rub the finger along the up- 

 per jaw; a frog has sharp teeth, 

 a toad none at all. The tadpoles of frogs, toads, and sala- 

 manders are much alike. In toad's spawn the eggs lie in 

 strings inclosed in jelly ; frogs spawn is in masses (Fig. 248). 



FlG. 261. Position of legs in tail- 

 less (A) and tailed (B) amphibian. 



