CONTENTS 



I. The Darwinian and Other Theories 



about Physical Life . ... . 1 



II. Reproduction and Heredity . . 34 



III. The Unicellular Micro-organisms 



the Oldest and Still the Largest 

 Division of the Living King- 

 dom 57 



IV. The Metazoa, or the Multicellular 



Forms of Life .... 93 



V. The Great Food Question . . 118 



VI. Adaptations 133 



VII. As to Ourselves 153 



