ORGANIC EVOLUTION 183 



muscle segments. A number of similar grooves may be 

 seen on the sides of the tail, especially at its base. The 

 surface of the skin is covered with the very minute openings 

 of pores from the large skin glands within it. These pores 

 are visible with a lens. These glands pour out the secretion 

 which keeps the skin moist and enables the salamander to 

 get its oxygen, as the worm does, in a large part by direct 

 absorption . It depends far less on its lungs for air than 

 do the higher vertebrates. Some vestiges of its early 

 aquatic life are preserved in the rudimentary webbing 

 between the bases of the toes, and in the flattening of the 

 tail, which is still put through superfluous sculling motions 

 when the salamander tries to run on land. 



At the tip of the snout a pair of small nostrils will be seen, 

 each with a blackish valve-like flap attached to its hind 

 margin within, and if the mouth be held open widely, the in- 

 ner openings from these nostrils may be seen on its roof at 

 the rear of the palate. On the floor of the mouth lies a fleshy 

 tongue, attached along its middle line, its edges lying free; 

 at the rear of the mouth, the pharynx, with its walls con- 

 verging to the esophagus, penetrated by abundant minute 

 blood vessels, which give to it something of the character of 

 a respiratory organ. In the lungless salamanders this 

 organ is better developed to serve that function. On the 

 floor of the pharynx is the glottis, the gateway to the lungs, 

 a narrow longitudinal slit with closely appressed cartilagi- 

 nous lips. Very minute and numerous teeth may be found 

 on the edges of the jaw by scraping it with a finger-nail or 

 with a needle, and two patches of palatine teeth may be 

 found farther back in the roof of the mouth. 



Internal features. Upon looking inside the body of the 

 salamander it is at once apparent that the main general 

 features of structure that were found to characterize the 

 earthworm, are repeated here. There is a compound- 



