CONTENTS. 



To what Extent does the Theory of Tropisms throw Light on the Behavior 



of Lower Organisms ?.......... 91 



Essential Points in the Theory of Tropisms, ...... 92 



Reactions to Mechanical Stimuli, ........ 94 



Reactions to Chemicals, . . . . . . . . . . 96 



Reactions to Heat and Cold, 98 



Reactions to Changes in Osmotic Pressure, ...... 98 



Reactions to Light, ........... 98 



Reactions to Gravity, 100 



Reactions to Electricity, .......... 100 



Resume* and Discussion, .......... 103 



Summary, 106 



90 



