1897.] The Biologie Origin of Mental Variety : 15 
thus, again, is a practical region of investigation. Already 
there is enlivened interest in the subject, and results of great 
value are being reached along the whole line of our several 
senses; results which, indeed, as a good numbcr of eminent 
scientists are likely to claim, leave no doubt, even now, as to 
how we should decide regarding this region of our perplexity. 
Should this happy consummation be reached, we should 
then have but our two primary propositions to decide between. 
And here, also, we have not only a legitimate field, but one 
regarding which it is probable the world of Science already 
has abundant data to give substantial conclusions, when once 
its importance is appreciated. In truth I have not, from the 
first, lost sight of or neglected the great value of the work 
done and being done in the field of Comparative Sense 
Organs; nor have I thought so much of the task being insur- 
mountable, of determining whether all our senses date from the 
beginning or not, as of the problem being too grave and far 
reaching for me to seem to treat it either lightly, or dogmatic- 
ally within the short space I have been able, here, to devote to 
it. 
It seems, therefore that our categories of doubt are likely to 
narrow to a substantial conclusion, even if the present aspect 
of Evolutionary Science should in no way broaden. But here, 
again, our problem is bright with promise; for its horizon is 
sure to broaden. And in setting down how this is likely to 
happen, I beg that my few concluding words, because of the 
importance of the subject, may be given special emphasis. 
However, natural the explanation may be, it still remains sig- 
nificantly true that the modern Science of Biology, wonderful 
as it is, has yet hardly progressed beyond the bare facts of 
Comparative Anatomy. These have been set up, like mile- 
stones, showing us where the course of Animal Morphology has 
run. But the Physiological processes, explaining how the course 
was run, remain nearly as unknown, and as little considered as 
before the day of Darwin. That Biologic Evolution can 
never be an understood fact until these physiological processes 
are given due study, is, among Scientists of first rank, just 
beginning to be appreciated. When fully appreciated as, it 
