158 COMPARATIVE ZOOLOGY. 
means of an elastic skin connecting the shoulder and 
wrist, which is stretched when the wing is expanded. 
Fig. 124.—Flamingoes taking Wing. 
Besides Insects and Birds, a few other animals have the 
power of flight, as Bats, by means of long webbed fingers ; 
Flying Fishes, by large pectoral fins; and Flying Reptiles, 
Flying Squirrels, and the like, by membranes between the 
fore and hind legs. 
(3) Locomotion on Solids. — This requires less muscular 
effort than swimming or flying. The more unyielding 
the basis of support, the greater the amount of force left 
to move the animal along. The simplest method is the 
suctorial, the animal attaching itself to some fixed object, 
and then, by contraction, dragging the body onward. But 
the higher and more common method is by the use of 
bones, or other hard parts, as levers. 
The Star-fish creeps by the working of hundreds of 
tubular suckers, which are extended by being filled with 
fluid forced into them by little sacs. The Clam moves 
by fixing and contracting a muscular appendage, called 
a “foot.” The Snail has innumerable short muscles on 
the under side of its body, which, by successive contrac- 
tions resembling minute undulations, enable the animal 
to glide forward apparently without effort. The Leech 
