BawDeEN, Psychological Theory of Evolution. 269 
results of such experiment show how difficult it is to devise 
problems which shall be at once congruous with the life of the 
lower animal and at the same time definite enough to prove of 
any scientific value. 
Summing up the main points we have covered so far, we 
have seen that the evolution of consciousness has been condi- 
tioned by factors of organic tension arising in connection with 
the attempt to solve crucial life problems, the criterion for the’ 
presence of consciousness in an organism being the possession 
of ability to vary the means employed in the adaptation, the 
ability to use this rather than that existent means to get a de- 
sired end. 
We come now to the second main consideration, as to the 
probable stages in the evolution of consciousness. The first 
question to be asked here, I suppose, would be as to the veg- 
etable world. Are plants conscious? We have criticized the 
view that denies all consciousness to the lower organisms. But 
we need not fall into the opposite error of supposing that the 
organism is necessarily always conscious. It is evident that 
many types which have deviated from the onward movement of 
evolutionary growth or have distinctly retrograded, will no 
longer present the conditions of struggle or tension requisite 
for the presence of consciousness. HERBERT SPENCER has gen- 
eralized the truth that motion, that activity, always follows the 
line of least resistance. Now the line of least resistance is the 
line or path of habit, of automatic action. It is for this reason 
that motion is rhythmic. The mechanized act is necessarily 
rhythmical, since any variant element would interfere with the 
smoothness of the coordination and thus call forth conscious- 
ness. Where an organism becomes adapted to a relatively fixed 
environment with little or no occasion for variation in the means 
necessary for the adaptation, consciousness will subside if not 
vanish altogether. The process of adjustment becoming auto- 
matic, attention, or consciousness, is no longer needed and ac- 
cordingly disappears. In this way among the lowest organisms 
all mind may have passed into the reflex stage after adapting the 
species to its environment, 
