256 BIOLOGY FOR BEGINNERS 



speed of the tongue is so great as almost to elude the sight, so it all makes 

 a very efficient food getting device. 



Usually the frog jumps at the same time it extends its tongue, thus increas- 

 ing its range very greatly. 



Toads also have the same adaptation, and some salamanders are even better 

 provided. 



Fig. 5 shows the position of rest in the water, with the prominent eyes and 

 anteriorly placed nostrils, just above the surface. In this position, either at 

 rest on the bottom, or afloat with hind legs extended, the frog is almost invisible 

 and thus escapes its enemies. 



Note the inturned front feet, mere props and the hind legs, folded ready to 

 swim or leap on the instant. 



that the eye cannot see the motion; the insect sticks to it and is 

 instantly thrown back within the capacious jaws, just where a 

 set of teeth on the roof of the mouth will hold and crush it. There 

 are no teeth on the lower jaw, as they would interfere when the 

 tongue was thrown out over them. Those on the upper jaw are 

 small, and in toads both sets are lacking entirely, as the real organ 

 of prehension in either case is the remarkable tongue. 



As we look inside the frog's mouth the nostril openings can be 

 seen near the anterior of the upper jaw; the tongue folded back 

 occupies the floor of the lower jaw; farther back at the sides are 

 the openings of the eustachian tubes from the ears; and at the 

 extreme rear, in the middle, can be found the wide gullet and slit- 

 like opening of the breathing tube or trachea. The walls of the 

 throat are loose and can be greatly expanded with air when the 

 frog is calling, thus acting as resonating chambers. This gives 

 great volume to the sound for which all frogs are noted. 



Other Organs. The eye of the frog is one of the most beautiful 

 in all the animal kingdom, having the black pupil surrounded by a 

 handsome bronze colored iris of large size. It projects conspicuously 

 from the top of the head, but can be withdrawn, level with the 

 skull. It is protected by lids and an extra covering, the nictitating 

 membrane, which can be raised from below and probably protects 

 the eye when under water. 



The location of the nostrils at the very tip of the head, and the 

 high projection of the eyes enable the frog both to see and breathe 

 while the rest of the body is covered by water. When in this 



