CONTENTS 
CHAPTER I. 
INTRODUCTORY . ‘ < x 
CHAPTER II. 
CLASSIFICATION q . , ‘ . s 
CHAPTER IIL. 
MORPHOLOGY . r ‘ ‘i . ¢ ° * 
CHAPTER IV. 
EMBRYOLOGY 
CHAPTER V. 
PALZONTOLOGY P 5 : ‘ A " 
CHAPTER VI. 
GEOGRAPHICAL DISTRIBUTION . : . . 
CHAPTER VII. 
THE THEORY OF NATURAL SELECTION 
CHAPTER VIII 
EVIDENCES OF THE THEORY OF NATURAL SELECTION 
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23 
5° 
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