CONTENTS 



/ I. INTRODUCTION 13 



v II. THE SYMMETRY RELATIONS OF THE ANIMAL BODY AS THE START- 

 ING POINT FOR THE THEORY OF ANIMAL CONDUCT 19 



III. FORCED MOVEMENTS 24 



IV. GALVANOTROPISM 32 



i/' V. HELIOTROPISM. THE INFLUENCE OF ONE SOURCE OF LIGHT... 47 



1. General Facts 47 



2. Direct Proof of the Muscle Tension Theory of Heliotrop- 



ism in Motile Animals 52 



3. Heliotropism of Unicellular Organisms 62 



4. Heliotropism of Sessile Animals 63 



VI. AN ARTIFICIAL HELIOTROPIC MACHINE 68 



VII. ASYMMETRICAL ANIMALS 70 



VIII. Two SOURCES OF LIGHT OF DIFFERENT INTENSITY 75 



IX. THE VALIDITY OF THE BUNSEN-ROSCOE LAW FOR THE HELIO- 

 TROPIC REACTIONS OF ANIMALS AND PLANTS 83 



X. THE EFFECT OF RAPID CHANGES IN INTENSITY OF LIGHT 95 



XI. THE RELATIVE HELIOTROPIC EFFICIENCY OF LIGHT OF DIFFER- 

 ENT WAVE LENGTHS 100 



XII. CHANGE IN THE SENSE OF HELIOTROPISM 112 



XIII. GEOTROPISM 119 



XIV. FORCED MOVEMENTS CAUSED BY MOVING RETINA IMAGES: 



RHEOTROPISM : ANEMOTROPISM 127 



XV. STEREOTROPISM 134 



XVI. CHEMOTROPISM 139 



XVII. THERMOTROPISM 155 



XVIII. INSTINCTS 156 



XIX. MEMORY IMAGES AND TROPISMS 164 



LITERATURE 173 



9 



