28 LIFE IN THE PRIMITIVE OCEAN 



the contrary, it is most important. What I want 

 especially to give in this little work is the general 

 machinery of evolution, the broad principles of the 

 subject. And this constant change of land and water 

 is a most important part of the machinery of the 

 evolution of life. You might poetically imagine it as 

 the struggle of the land to free itself from the water. 

 In the course of time it has thrown the bulk of the 

 waters into deep ocean beds, and has reared itself in 

 high mountain-chains and broad continents. The 

 changes which this restless struggle has brought about 

 from age to age have very deeply inlBuenced the 

 development of life, as we shall see. 



But first we have to introduce life itself. It ap- 

 peared at a very remote date in the warm, shallow 

 ocean of the primitive earth. How long ago that was 

 we cannot say. Most geologists would say between 

 fifty and a hundred million years ago. There is, 

 however, a new school which professes that what are 

 called the "radio-active" minerals (minerals whose 

 atoms break up, like those of radium) in the older 

 rocks show that the earth must be more than a 

 thousand million years old. There is really no reason 

 why we should be in a hurry to decide how old the 

 earth is. It is enough that the story of life on it 

 began at least tens of millions of years ago. 



Where did the first living things come from, and 

 what were they like? That is a mxOre interesting 

 question. Unfortunately, science is not yet able to 



