224 



FIRST LHSSONS IN ZOOLOGY 



ma)- "assume almost instantl)' shades varying from a 

 beautiful emerald to a dark and iridescent JDronze color." 

 About lOOO lix-ini;- species of snakes are known. Usu- 

 ally the>' have the body reL,ailarly cylindrical, and without 

 distinct dixision into bod)--rcgions. Legs are wanting, 

 locomotion l)eing effected by the help of the scales and 

 ribs. No snake can mo\'e forward on a perfectly smooth 

 surface, and no snake can leap. In some forms, such as 



Fig. 183. — Tlie yopliL-r-snake, rUiiophis lullona. (Photoi^'niph from life by 

 J. (J. Snyder.) 



the pytlions, external rudiments of the hind limbs are 

 present, but do not aid in locomotion. 'bhe mouth is 

 large and distensible, so that prey of considerably greater 

 size than tlie normal diameter of the snake's body is fre- 

 quent!}' swallowed whole. The sense of taste is very 

 little if at all developed, as the food is swallowed without 

 mastication. The tongue, which is protrusiblc, and usu- 

 ally red or blue-black, ser\'es as a special organ of touch. 

 Hearing is poor, the ears Ijeing \'er)' little dc\-eloped. The 

 sense of sight is also probabl)- nr)t at all keen. Snakes 

 rely chiefly on the sense of smell for finding their prey 

 and their mates. 'i"he colors of snak'es are often brilliant 



