968 The American Naturalist. [ December, 
ently incorporated into our psychic existence. They must, therefore, 
explain the variety of our psychic elements, and the origin of their 
connection with the central mechanisms on which they now depend, 
and with their respective sense organs. Consequently, also, they 
must furnish a key for deciding between our two rival theo- 
ries of the origin of our psycho-physical organism. And alto- 
gether, a study of this subject must unlock to us wide and un- 
forseen fields of scientific truths. 
That the evolutionary values of his various “energies” 
should not have been perceived by Miiller is not surprising, 
but that they remain unconsidered to-day can only be ex- 
plained by the vagueness of current notions regarding them ; 
and it must now be our task to come to a realization of the 
conditions which they involve. 
Bearing in mind that, as is now demonstrable, the molecu- 
lar basis underlying each one of the sense-elements of which 
our brain is capable comprises billions of variable physical 
constituents, we may first note that this truth must have its 
influence within the sphere of Spontaneous Variation. We do 
not yet fully know the laws which govern variation, and there 
is difference of opinion as to the role it plays in developing or- 
ganisms. But at least the followers of Weissmann should ap- 
preciate that not all neural “ energies” of such vast complex- 
ity could have equal chances of advent, and that this fact 
must have been a major condition in the origin of those dif- 
ferent classes of sensation with which we are now equipped. 
Secondly, we may appreciate that the variants in question 
must constitute determining factors of organization within the 
circle of Nutrition. Not only must our intricate brain com- 
ponents be born into our organism, but they must be main- 
tained there in face of exhaustion and fatigue. Loss of the 
thyroid gland demonstrates to-day how special are the ingre- 
dients necessary for maintaining the general functions of intel- 
ligence; and there is ample room within the mysteries of 
Aphasia to suspect that the requirements are even yet more 
specific that must be provided within localized regions of the 
cortex for our different senses. Every notion of modern 
science suggests that these activities must be specifically com- 
