400 The Movements of Plants 
are dissimilar in the two cases) We must come back, in fact, to 
Darwin’s comparison of plants to animals. In both there is per- 
ceptive machinery by which they are made delicately alive to their 
environment, in both the existing survivors are those whose internal 
constitution has enabled them to respond in a beneficial way to the 
disturbance originating in their sense-organs. 
