206 THE HAUNTS OF LIFE 
the shore, for the conditions of life are more 
than half terrestrial when the tide is out. 
In his fine introduction to Zoology, called 
Animal Life, Professor F. W. Gamble gives a 
vivid picture of the four chief kinds of animal 
locomotion. He takes the case of aman ina boat 
on a river, who can make headway against the 
current in four ways. (1) He may take a boat- 
hook and, fastening it to the roots on the bank, 
Fic. 22.—A JERBOA. 
A leaping Biped belonging to the Rodent Order. 
pull himself forward. So does a star-fish pull 
itself up a rock; so does a leech pull itself for- 
ward when it fixesitsmouth. This is the pulling 
method. (2) He may take a pole, or an oar for 
that matter, and, pressing it against the bed of 
the stream, lever himself forward. So does 
the beetle push its legs against the ground; so 
