CONTENTS. 



PAGE. 



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, IO o 



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



RSsume' and Discussion IC >3 



Summary IO 6 



90 





