CONTENTS 



CHAPTER PAGE 



I. CONDITIONS OF ANIMAL LIFE . ..... 1 



II. PRINCIPLES OF CLASSIFICATION . ... .13 



III. THE SIMPLEST ANIMALS OR PROTOZOA .... 22 



IV. THE SLIGHTLY COMPLEX ANIMALS OR SPONGES . . 33 



V. THE CCELENTERATES 43 



VI. THE WORMS 59 



VII. ANIMALS OF UNCERTAIN RELATIONSHIPS ... 83 



VIII. MOLLUSKS .89 



IX. THE ARTHROPODS 109 



X. ARTHROPODS (continued} CLASS INSECTS . . . 130 



XI. ARTHROPODS (continued) CLASS ARACHNIDA . . . 143 



XII. ECHINODERMS 150 



XIII. THE CHORD ATES 161 



XIV. THE FISHES 164 



XV. THE AMPHIBIANS 182 



XVI THE REPTILES 192 



XVII. THE BIRDS 209 



XVIII. THE MAMMALS ........ 232 



XIX. THE LIFE CYCLE 254 



XX. THE CROWDS OF ANIMALS AND THE STRUGGLE FOR 



EXISTENCE 281 



XXI. ADAPTATIONS 290 



XXII. ANIMAL COMMUNITIES AND SOCIAL LIFE .... 314 



XXIII. COMMENSALISM AND PARASITISM 335 



XXIV. PROTECTIVE RESEMBLANCES AND MIMICRY . , . 350 



