CONTENTS. 



PAGE. 



To what Extent does the Theory of Tropisms throw Lighten 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 



Risume* and Discussion, .......... 103 



Summary, ............ 106 



90 



