166 THE MEANING OF EVOLUTION 
active, or, as we say, they are dormant. In such con- 
ditions they become covered with a tough skin, almost 
a shell, and their protoplasm is itself nearly dry. 
Under these circumstances the life processes hardly 
continue at all. The protozoa, as these small animals 
are called, tolerate drought for a time; but they only 
live, in any sense worth calling living, when water is 
abundant and is neither very warm nor very cold. 
It is safe to say that the early life of the world formed 
in the oceans of the time. So absolutely is the habit 
fixed upon cells of protoplasm that even to-day the 
activities of the cells of higher animals depend upon 
the presence of moisture. The cells of our own bodies 
are to-day living, as it were, in an ocean. Everyone 
can remember far enough back to recall some time at 
which a tear slipped from his own eye onto his own 
tongue; we know our tears are salt. The tongue has 
tasted, undoubtedly, the perspiration from the lip on 
more than one summer day; this perspiration tasted as 
salt as the tear itself. The lymph that constitutes the 
“water” of a so-called “water blister” is also salty, 
and even the little blood one gets into his mouth in 
trying nature’s method of stanching the flow from a 
cut finger gives the impression that it contains a little 
salt. Every fluid of the body is salty, and every cell 
of the body is bathed in salt water. It is too long 
since the ancestors of our cells swam in the seas of the 
