688 The American Naturalist. [July, 
and the circular reaction which underlie the entire book. These 
chapters, although of considerable intrinsic value, are superfluous so far 
as the main object of the book is concerned, in that their contributions to 
it might have been much more clearly put and in briefer compass. It 
is in the last chapter, on Suggestion, that the principal of dynamogen- 
esis is most clearly stated: ‘The principle of contractility recognized 
in biology simply states that stimulations to living matter—the pro- 
toplasm of the higher vegetable and animal structures—if they take 
effect at all, tend to bring about movements or contractions in the 
mass of the organism. This is now also safely established as a phe- 
nomenon of consciousness—that every sensation or ingoing process 
tends to bring about action or outgoing process.” (P. 166.) The 
movements thus produced may simply be repeated, thus forming a 
habit. But many of them “seem to beget new movements by a kind 
of adaptation of the organism—movements’ which are an evident 
improvement upon those which the organism has formerly accom- 
plished.” How is this done? This introduces us to the main 
problem of the book—that of Accommodation. 
The answer is found in the Law of Excess. Of all the stimuli to 
which the organism is exposed some are advantageous. These 
heighten vitality and thereby increase the amount of motor reaction. 
In the case of advantageous stimuli the reaction is expansive, towards 
the source of stimulation, but the disadvantageous produce contrac- 
tions, away from the source of stimulation. It is evident that the 
expansive movements are best fitted to secure the repetition of the 
stimulus, and the excessive discharge greatly increases this proba- 
bility. If any one of these movements proves successful, there is a 
second excess discharge, but the second tends to pass out by the 
channels of the successful movement. This gives us the nucleus of a 
habit. The law that advantageous stimuli produce expansive move- 
ments and disadvantageous contraction is doubtless due to natural 
selection. (Pp. 199 et seqq.) The admission or denial of the inheri- 
tance of acquired traits would not affect this theory. And, since it 
represents selective reaction as part of the original endowment of 
life, and since this selective reaction is the organic analogue of pleas- 
ure and pain, we may say “that life began with consciousness, that is, 
with feelings of pleasure and pain. This position preserves the 
criterion of mind, making it also the criterion of life, and so assumes 
an absolute phylogenetic beginning of both life and mind in one.” 
(P. 213.) From the preceding discussion the relation of Habit and 
Accomodation comes clearly to view. “ Habit expresses the tendency 
