Xll TABLE OF CONTENTS. 



PAGE 



Direct and Indirect Development Metamorphosis . . 193 



Oviparous and Viviparous Animals 194 



Ovo-viviparous Animals 194 



No Sharp Line to be Drawn between Oviparous and 



Viviparous 195 



Summary of the Facts of Ontogeny 195 



III. Relations of Animals to One Another 198 



General Relations 198 



I. Relations between Individuals of the Same Species .... 198 



Colony Formation 198 



Colony Formation by Fusion 199 



Colony Formation by Incomplete Division and Budding . 199 



Community of Functions 200 



Polymorphism 200 



State Formation 201 



II. Relations between Individuals of Different Species . . . 202 



Causes of Close Relation 202 



Parasitism 202 



True Parasitism 202 



Degeneration Caused by Parasitism 203 



Modification of the Sexual Apparatus by Parasitism . . 203 



Ectoparasites and Entoparasites 204 



Symbiosis 205 



Occurrence of Symbiosis 206 



IV. Animal and Plant 207 



Distinction between Animal and Plant 207 



Doubtful Cases 207 



Distinction on a Physiological Basis 208 



Difference in Metabolism Not a Safe Criterion .... 208 



Cellulose not a Sure Test 209 



Distinction on a Morphological Basis 209 



Plant-cells have a Cellulose Membrane 209 



Transitions 209 



V. Geographical Distribution of Animals 210 



The Different Faunal Regions 210 



Climate Not the Only Consideration 210 



Factors in Distribution 211 



Difficulties of the Subject 212 



The Six Primary Regions 213 



Arctic and Antarctic Provinces 215 



The Distribution of Aquatic Animals 216 



Changes in the Fauna Conditioned by Depth 216 



The Plankton 216 



Distribution of Fresh-water Animals 217 



INDEX 219 



