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TABLE OF CONTENTS. 



PAGE 

 I 



INTRODUCTION WHAT is EVOLUTION ? . 



Original meaning of the term in scientific literature Evolu- 

 tion and Darwinism Evolution and theology Prevalence 

 of the evolutionary theory to-day. 



I. 



ARE SPECIES MUTABLE ? . . . -* ' ' . 22 

 Immutability of species Variation Causes of variation 

 Limits of variation Are species stable ? Sterility of hybrids 

 and fertility of mongrels Indirect evidence from the rela- 

 tions of animals ; From fossils, from reversions Summary. 



II. 



CLASSIFICATION OF THE ORGANIC WORLD . . 53 

 Existence and significance of a classification The explana- 

 tion of Cuvier The explanation of evolution The relation 

 of species expressed by a branching structure Reasons for 

 this conclusion Value of the tree-like classification Appli- 

 cation of the theory to the explanation of homology Ho- 

 mology in general Serial homology Rudimentary organs 

 Aborted organs Nascent organs Summary. 



III. 



LIFE DURING THE GEOLOGICAL AGES ... 89 

 Significance of the evidence Imperfection of the record 

 First appearance of life in the Silurian age Difficulty in 

 regard to time Absence of numerous generalized forms in 



