KAMA. 339 



and other small animals, but retires through the day into 

 water or rocky hgles. In the winter the frog hibernates in 

 pond-mud or in holes. 



The head is set upon the trunk with no neck and the 

 latter carries two conspicuous pairs of limbs. The mouthy 



when open, is a wide gaping fissure, literally 

 Futures extending "from ear to ear." At the tip of the 



" nose " is a pair of small external nares leading 

 into the olfactory or nasal sacs. Further back are the eyes, 

 and a little behind and below them are the tympanic mem- 

 branes of the ears or auditory organs. These are covered 

 with skin and appear as round surfaces. 1 he front limbs 

 have four digits, the thumb being absent. The hind limbs 

 have five long 'toes or digits with a web stretched between 

 them. The male Rana temporaria in the breeding season 

 has a thickened callosity on the first digit of each fore-limb. 

 Dorsal to the junction of the hind limbs and the trunk is a 

 single cloacal aperture. 



The whole body is enclothed in a loose moist skin, with 

 an entire absence of scales, hairs, or other exoskeleton. 



There are abundant skin-glands which serve 

 mentar7 ^^ ^^^P ^^ ^^^^ moist Under the skin are 



numerous blood-vessels which enable the skin 

 to assist in the function of respiration. 



The skin has scattered pigment of various colours, and 

 the frog has the power to adapt its general coloration to its 

 surroundings fairly rapidly. If the jaws be widely opened 

 the buccal cavity is exposed. The tongue is forked, free 

 behind and fastened at the front end ; it can be shot out 

 with great rapidity for catching insects.'^ The lower jaw^ has 

 no teeth, but a row of delicate teeth lines the upper. In 

 addition there are in the roof of the mouth two patches of 

 small vomerine teeth, so-called because they are on the 

 vomer bones. 



Just behind these teeth are paired internal nares leading 

 to the exterior by the nasal sacs and the external nares. 

 They serve for the introduction of air. Further back, near 

 the angles of the jaw, is found on each side a widely-open 

 passage, the Eustachian tube, leading almost at once into the 



* The tongue is protruded by the pressure of lymph forced into its interior by the 

 contraction of muscles, such as the mylohyoid. 



