CONTENTS xiii 



CHAPTER PAGE 



Evolution of the Horse 406 

 Evidence from Comparative Anatomy 408 

 Unity of Plan within a Group — Vestigial and Rudi- 

 mentary Structures — Comparisons of Organs and 

 Organ Systems — Continuous and Divergent Series 

 Evidence from Embryology 411 

 Evidence from Parasitism 413 

 Evidence from the Distribution of Animals 414 

 Barriers — Time — Food Supply — Number of Offspring — 

 Climate 

 Evidence from Histology and Physiology 416 

 The Origin of Life 418 



XII. The Science of Biology 421 



Origins 421 



Biology in the Seventeenth Century 422 



Biology in the Eighteenth Century 423 



The Cell Doctrine. Protoplasm 423 



Division of Biology 424 



The Relation between Biology and Other Sciences 425 



The Scientific Method 426 



Biology Today 429 



Experimental Technique 429 



Trends of Biology 430 



Abstract and Applied Biology 431 



Glossary 439 



Index 463 



