CONTENTS. 



CHAPTER I. 



THE NATURE OF ANIMAL LIFE. 



PAGE 



The characteristics of animals .. .. .. .. 2 



The relation of animals to food-stuffs . . 



the atmosphere , . . . . . . . 15 



energy 



CHAPTER II. 



THE PROCESS OF LIFE. 



Illustration from respiration . . . . . . . . 21 



nutrition .. .. .. .. 25 



The utilization of the materials incorporated 



The analogy of a gas-engine. Explosive metabolism . . 30 



CHAPTER III. 



REPRODUCTION AND DEVELOPMENT. 



Keproduction in the protozoa .. .. .. .. ..37 



Fission in the metazoa . . . . . . . . . . 41 



The regeneration of lost parts . . . . . . . . 41 



Keproduction by budding . . . . . . . . . . 42 



Sexual reproduction . . . . . . . . 42 



Illustration of development . . . . . . . . . . 51 



Parental sacrifice . . . . . . . . . . 56 



The law of increase . . 58 



CHAPTER IV. 



VARIATION AND NATURAL SELECTION. 



The law of persistence . . . . . . . . . . 61 



The occurrence of variations . . . . . . . . . . 63 



Application of the law of increase . . . . . 76 



Natural selection , 77 



