l66 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 



