Contents 
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 hcg Disuse . 
Reactions of the Organism to Poisons, etc. 
Regeneration 
CHAPTER XI 
TROPISMS AND INSTINCTS AS ADAPTATIONS 
CHAPTER XII 
SEx AS AN ADAPTATION 
The Different Kinds of Sexual Individuals 
The Determination of Sex 
Sex as a Phenomenon of Adaptation 
CHAPTER XIII 
SUMMARY AND GENERAL CONCLUSIONS . 
INDEX . . . . . . . 
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