196 ANIMAL FORMS 
carnivorous, and usually very voracious. The lizards espe- 
cially devour large quantities of insects and snails, together 
with small fishes and frogs. The latter figure largely in 
the turtle’s bill of fare, and in that of the snakes, which 
also capture birds and mammals. On the other hand, many 
of the reptiles prey upon one another; and they are the 
favorite food of hawks and owls and numerous water-birds, 
of skunks and weasels and many other animals, which look 
for them continually. Many of the turtles, owing to their 
protective armor, and the snakes because of their poison- 
ous bite or great size and strength, are more or less ex- 
empt, but this is not true of their eggs and young. The 
smaller species depend upon keenness of sense, agility, and 
inconspicuous tints. These latter may undergo changes 
according to the character of the surroundings, but usually 
only to a slight extent. The chameleons of the tropics 
and a similarly colored green lizard on the pine-trees in 
the Southern States are able to change with great rapidity 
from green, through various shades, to brown. — 
185. Respiration and circulation While still in the egg 
the young lizard develops rudimentary gills, and thus bears 
Fia. 118.—Dissection of lizard (Sceloporus). an., anal opening ; au., auricle ; crb.h., 
brain ; coec., intestine; kd., kidney ; l.Jng., left lung; Ur., liver } pn., pancreas ; 
sp.c., spinal cord ; spl., spleen ; st., stomach ; v., ventricle of heart. 
evidence to the fact that its distant ancestors were aquatic; 
but before hatching they disappear, and lungs arise, which 
