The Wit of the Wild 



they are in summer. Frogs kept in dry moss, 

 or such as have escaped into the room and dry 

 up, turn pale, regardless of light or darkness, 

 probably owing to a central, reflex, nerve- 

 stimulus. 



" Tree-frogs turn green as a result of the 

 contact with leaves. Dark frogs will turn green 

 when put into an absolutely dark vessel in 

 which there are leaves. This is reflex action, 

 and blinded specimens do the same. The princi- 

 pal centers of the nerves which control the chro- 

 matophores lie in the corpora bigemina and in 

 the optic thalami of the brain. When these 

 centers are destroyed the frog no longer 

 changes color when put upon leaves, but if a 

 nerve, for instance the sciatic, be stimulated, 

 the corresponding portion of the body, in this 

 case the leg, turns green. Rough surfaces 

 cause a sensation which makes the frog turn 

 dark. . . . Biedermann concludes that the 

 * chromatic function of frogs in general de- 

 pends chiefly upon the sensory impressions re- 

 ceived from the skin, while that of fishes depends 

 upon the eye.' 



" All this sounds very well, but the observa- 

 tions and experiments are such as are usual in 

 physiological laboratories, and frogs, when ob- 

 served in their native haunts, or even when kept 



$ 222 fo> 



