92 VITALISM AND SCHOLASTICISM 



explained as tactisms, and as re-actions to cer- 

 tain chemical or physical forces, it ^is not pos- 

 sible to explain all the phenomena of life or 

 of irritability in these terms. 



NOTE. It may be noted that Jennings in 

 his work on Animal Behaviour explains all these 

 Tactisms by Trial and Error and Avoidance 

 Reactions. The same seems to hold of Tropism, 

 i.e., movements of plants due to unequal 

 growth. Growth is never rectilinear but 

 wobbles. But it tends to wobble in the most 

 favourable course, and wobbling away from 

 such a course is inhibited. 



