584 
constitute a distinct and novel series of 
problems. In many cases they are so re- 
markable and so unexplainable that cer- 
tain German writers, such as Driesch, have 
taken the ground that they spring from the 
ultimate constitution of living matter and 
are incapable of analysis. At the same 
time it has been recognized that these adap- 
tations are purely individual, transitory or 
ontogenic, leaving for a long time, at least, 
no perceptible influence upon the heredi- 
tary constitution of the organism. What 
may be called the‘ traditional’ side of these 
adaptations impressed itself strongly upon 
Professor James Mark Baldwin in his studies 
of mental development, also upon Pro. 
fessor Lloyd Morgan in his studies of in- 
stinct. The latter, moreover, was one of 
the first among English selectionists to con- 
sider ‘determinate variation’ as a fixed 
problem which must be included in any 
evolution theory. Thus, independently, 
Professors Baldwin and Morgan and myself 
put together the facts of individual adapta- 
tion with those of determinate variation 
into an hypothesis which is in some degree 
new. The first illustration which I used 
was that of the creation of an ‘arboreal 
man’ out of any present terrestrial race by 
the assumption of an exclusively tree life. 
This life would be profound in its influences 
upon each generation producing what would 
be pronounced by zoologists a distinct spe- 
cific type. In course of many thousand 
years such a type might become hereditary 
by the slow accumulation of arboreal adap- 
tive and congenital variations. The basal 
idea of it was contained in the Romanes 
Lecture by Weismann, but it was not 
brought out with emphasis, nor subse- 
quently developed by that distinguished 
author. 
The position taken by Poulton, Morgan 
and Baldwin that individual adaptation is 
in itself a result of natural selection can- 
not be demonstrated, except in cases where 
SCIENCE. 
(N.S. Vou. VI. No. 146. 
it is evident that such adaptation is in re- 
sponse to revived ancestral experience. In 
many instances, individual adaptation, as in 
cases of regeneration, is of advantage to 
the individual, but decidedly detrimental 
to the race, where it would result in the 
perpetuation of the progeny of a maimed 
or imperfect embryo. 
Organic selection is the term proposed 
by Professor Baldwin and adopted by Pro- 
fessor Morgan and myself for this process 
in nature which is believed to be one of 
the true causes of definite or determinate 
variation. The hypothesis is briefly as 
follows: That ontogenetic adaptation is 
of a very profound character. It en- 
ables animals and plants to survive very 
critical changes in their environment. Thus 
all the individuals of a race are similarly 
modified over such long periods of time that 
very gradually congenital or phylogenetic 
variations, which happen to coincide with 
the ontogenetic adaptive variations, are se- 
lected. Thus there would result an appar- 
ent but not real transmission of acquired 
characters. 
This hypothesis, if it has no limitations, 
brings about a very unexpected harmony 
between the Lamarckian and Darwinian 
aspects of evolution, by mutual concessions 
upon the part of the essential positions of 
both theories. While it abandons the trans- 
mission of acquired characters, it places in- 
dividual adaptation first, and fortuitous 
variations second, as Lamarckians have 
always contended, instead of placing sur- 
vival conditions by fortuitous variations 
first and foremost, as selectionists have 
contended. 
This hypothesis has been endorsed by 
Alfred Wallace. It appears to me, how- 
ever, that it is subject to limitations and 
exceptions which go far to nullify its 
universal application. This is especially 
seen in the fact that the law of determinate 
variation is observed to operate with equal 
