CONTENTS xv 



CHAPTER PAQE 



Nature of Organic Response 246 



Electric Response 247 



Individual Response to Unsymmetrical Stimuli . ' 248 



Adaptive Response 253 



Immunity . 255 



Morphogenetic Response 256 



Non-adaptive Morphogenetic Response . .257 



Influence of Food 258 



General Adaptation 259 



Some Types of Adaptation 260 



Aquatic Organisms 260 



Aerial Adaptations ...... 262 



Subterranean Adaptations .... 263 



Protective Adaptations 266 



Protective Coloration .... 267 



Specific Resemblance .... 268 



Aggressive Resemblance .... 269 



Mimicry 269 



The Care of the Young .... 272 



Environmental Adaptations of Plants . . . 274 



Adaptations for Seed Dispersal . . . 278 



Associations of Animals 279 



Commensalism 280 



Parasitism in Protozoa 283 



Parasitism in Worms . . . . . . 285 



Parasitism, in Insects 287 



Sacculina . . . . . . . . . 289 



Associations among Plants 290 



Lichens 291 



Parasitism in Plants 292 



Associations of Plants and Animals .... 293 

 Grafts .... ,294 



IX. SPECIES AND THEIR ORIGIN 



296 



Meaning of Species 296 



Polymorphism 301 



Elementary Species and Linnaean Species . . 305 



