Contents xiii 



CHAPTER X 



The Origin of the Different Kinds of Adaptations 

 Form and Symmetry 

 Mutual Adaptation of Colonial Forms 

 Degeneration .... 

 Protective Coloration 

 Sexual Dimorphism and Trimorphism 

 Length of Life as an Adaptation 

 Organs of Extreme Perfection . 

 Secondary Sexual Organs as Adaptations 

 Individual Adjustments as Adaptations 

 Color Changes as Individual Adaptations 

 Increase of Organs through Use and Decrease through Disuse 

 Reactions of the Organism to Poisons, etc. 

 Regeneration 



PAGE 

 340 

 340 

 3SO 

 352 



357 

 360 



37° 

 37i 

 372 

 375 

 375 

 376 



377 



379 



CHAPTER XI 



Tropisms and Instincts as Adaptations 382 



CHAPTER XII 



Sex as an Adaptation 414 



The Different Kinds of Sexual Individuals .... 414 



The Determination of Sex 422 



Sex as a Phenomenon of Adaptation ..... 439 



CHAPTER XIII 



Summary and General Conclusions 452 



INDEX 465 



