102 LIFE AND HER CHILDREN. 
draws itself in and out, showing a new expedient used 
by an animal in which the tube-feet are wanting. 
These and many other wonderful adaptations are 
open to all to study, but we must not linger over 
them here. One marked step we have made in this 
division we have advanced from mere floating or 
fixed animals to creatures able to wander freely over 
the floor of the ocean. The children of life have 
now got their feet upon the ground, but not yet 
their heads above water. In fact they have as yet 
no heads to put anywhere. Eyes, ears, mouths, and 
feet we have met with, but no heads, nor have any 
of these animals been able to live out of their watery 
home. 
But soon a new prospect opens before us, and in 
the mollusca or soft-bodied animals, and the worms, 
we shall begin to enter upon earth-life. Not sud- 
denly, however, for all new powers are of slow growth, 
and through many chapters yet we shall find the 
largest number of each group clinging to their old 
ocean home, and only here and there air-breathing 
and head-crowned forms mingling in the throng. 
