12 Contents 



CHAPTER PAGE 



XII. Experimental Biology, Mechanism Versus Vitalism 

 Continued. Tropisms, Instincts and Intelligence. 

 Hormones. Artificial Fertilization 301 



XIII. Color in Nature. Colors of Flowers and the Inter- 



relation OF Flowers and Insects. Colors of 

 Animals and Their Physico-chemical Causes. The 

 Theories of Pjiotective Coloration, Warning and 

 Alluring Colors, Mimicry and Recognition Marks 330 



XIV. Aquatic Biology. Oceanography, Life of the Sea and 



Its I']nvikonment. Biology of Inland Waters. 

 Methods of Studying Aquatic Life 349 



XV. Economic Biology. Dependence of Man upon Nature. 

 Ignorance of Nature the Cause of Economic Loss. 

 Conservation and Increase of Natural Resources . 385 



XVI. Biology and Medicine. Microscopic Life and Its Re- 

 lation to Human Health. The Role of Animals in 

 Spreading Disease. Animal Experimentation and Its 

 Contributions to Human Welfare. The New Medi- 

 cine, Safeguarding the Health of the Nation . . 440 



XVII. The Outlook. Some Unsolved Problems of Biology. 



Possibilities of Larger Service 478 



