23 6 TEXT-BOOK OF ZOOLOGY 



ment of capture. This organ is long and vermiform, club-shaped in 

 front, and can be protruded to half the length of the animal's body, 

 with lightning speed. The tongue hits an insect with the utmost 

 precision, the prey adhering to the club-shaped end, which is covered 

 with a glutinous substance, and being thence conveyed into the mouth. 

 (Compare woodpecker.) The Spaniards take advantage of this dexterity 

 of the animal in the capture of insects by employing it (as well as the 

 gecko) in their houses as a living fly-trap. 



ORDER III. : SNAKES (OPHIDIA). 



BODY vermiform, covered with scales or scutes. Limbs and pectoral and 

 pelvic arches absent. Bones of the face generally very movable. Teeth 

 not lodged in sockets. Eyelids absent. 



i. Non-Venomous Snakes. 



The Ringed Snake (Tropidonotus natrix). 

 (Length up to nearly 5 feet.) 



A. Locomotion and Locomotor Organs. 



1. The ringed snake, like all other members of the order, is limbless, 

 and accordingly (see lizard, Section E, 2 a) its body is elongated and 

 vermiform. It progresses by a lateral sinuous or undulatory movement 

 of the whole body, a method which has been described in the case of the 

 lizard. Its progress in the water is effected in a similar manner. 



For this kind of motion an extremely flexible body, or what amounts 

 to the same thing, an extremely flexible vertebral column, is required. 

 (Compare with other classes of Yertebrata.) This flexibility is attained 

 by the presence of a very large number of vertebra, which, moreover, 

 are movably articulated to each other. The anterior face of the 

 centrum of each vertebra is concave, and receives the spherical posterior 

 surface of the centrum of the preceding vertebra, which moves freely 

 in the concavity, as the humerus of mammals moves in the shoulder- 

 joint (ball-and-socket joint). 



2. The absence of limbs is compensated by the presence of a large 

 number of ribs, on the free blunt ends of which the snake in the 

 absence of a sternum glides along as upon so many legs. For this 

 purpose the ribs are united by ball- and- socket joints (see Section 1), with 

 the vertebrae, and moved in a backward and forward direction by means 

 of numerous muscles arising from the body walls. At each undulation 

 of the body the ribs are drawn forward and again forced backwards like 



