1890.}- 7 ` The Evolution of Mind. 905 
memory, —merely the habit of identical response to identical 
stimuli, on the principle that energy in organic substances most 
easily traverses accustomed channels. But it is not easy to 
believe in a stimulus which is not consciously felt producing any- 
thing but an undesigned, indefinite movement; and memory, 
conscious or unconscious, could only repeat it. A movement 
directly related to the satisfaction of sensation could only origi- 
nate in a sensation, and the unconscious memory would repeat it 
blindly on the occasion of the experience of an identical stimu- 
lus. So soon as conscious memory should appear, the possibility 
of more exact adaptation or design in an act would appear. 
Variations in the act appropriate to variations in the stimulus 
would become possible. We may suspect conscious memory in 
the exact ratio of the appearance of predication under slightly 
varied circumstances, when narrower resemblances and differences 
are evidently to be taken into account. In such cases comparisons 
of memories are necessary, and rudimentary classification begins. 
Mr. Romanes, in his work, “ Mental Evolution in Animals,” 
gives the following as his “ criterion of mind”: “The criterion of 
mind, ejectively considered, consists in the exhibition of Choice, 
and the evidence of Choice we found to consist in the performance 
of adaptive action suited to meet circumstances which have not 
been of such frequent or invariable occurrence in the life-history 
of the race as to have been specially and antecedently provided 
for in the individual by the inherited structure of its nervous sys- 
tem.” This is an excellent definition of mind which has reached 
the stage of predication. But for purposes of classification, I 
should include all the phenomena of consciousness in the domain 
of mind, as distinguished from that of no-mind or physical energy. 
Such is the custom of metaphysical writers, who include percep- 
tion within the range of their science, as it seems to me properly. 
The simple sensations should be included within the realm of 
mind. Here also should be included the “ subconscious” state, 
with which we are all more or less familiar. Thus an impression 
may be made on the mind while its principal consciousness is 
otherwise occupied, and this impression may lead to attention, 
which is followed by a more distinct impression, if the cause of it 
