CHARACTERS OF VERTEBRATES. 165 



The animal has a head with a slight constriction between 

 it and the body. The head has two eyes, capable of being 

 closed by movable lids. The mouth opens transversely; 

 that is, the lower jaw is on the under part of the head, and 

 moves up and down. In the insects and Crustacea, the jaws 

 are on the sides of the head and open sideways. The 

 jaws have minute teeth, and in large salamanders the teeth 

 can be felt by rubbing the finger along the edge of the 

 mouth. On the front of the head there are two holes repre- 

 senting the nostrils. The creature has four short legs, a for- 

 ward pair and a hinder pair ; it has short feet also, with four 

 toes on each forward foot, and five toes on each hinder foot. 

 The tail, which is quite as long as the body at its commence- 

 ment, is nearly as wide as the body, but tapers gradually, 

 and becomes flattened at its end. 



148. How different in every respect is this creature from 

 the animals thus far studied in this book ! and yet, if the sal- 

 amander is compared with a dog or cat, the characters men- 

 tioned above will be found in each. The cat has also a head 

 containing two eyes with movable lids ; the lower jaw is on 

 the under part of the head and moves up and down and the 

 mouth opens transversely ; it is furnished with teeth, there are 

 four legs with feet and toes, and the creature has a tail. But 

 there are also important differences between the two : the cat 

 has external ears, while the salamander has none, though it 

 has parts which enable it to hear. The cat's skin is covered 

 with hair and is dry, while the salamander has no hair upon 

 it and the skin is always moist. The cat has sharp claws, 



