586 
while the considerations now advanced only 
confer added significance and strength to 
Darwinian standpoint. 
I propose to devote the remainder of the 
time at my disposal in support of the con- 
clusion that the power of individual adap- 
tation possessed by the organism forms one 
of the highest achievements of natural 
selection, and cannot in any true sense be 
considered as its substitute. Professor 
Baldwin and Professor Lloyd Morgan 
thoroughly agree with this conclusion and 
have enforced it in their writings on or- 
ganic selection. The contention here urged 
is that natural selection works upon the 
highest organisms in such a way that they 
have become modifiable, and that this 
power of purely individual adaptability in 
fact acts as the nurse by whose help the 
species, as the above-named authorities 
maintain, can live through times in which 
the needed inherent variations are not 
forthcoming, but in part acts also as a sub- 
stitute, not indeed for natural selection, but 
for the ordinary operation by which the 
latter produces change. In this latter case 
natural selection acts so as to produce a 
plastic adaptable individual which can meet 
any of the various forces to which it is 
likely to be exposed by producing the ap- 
propriate modification, and this, it is 
claimed, is in many instances more valu- 
able than the more perfect, but more rigid, 
adjustment of inherent variations to a fixed 
set of conditions. 
A good example of the eminent advan- 
tages of adaptability in many directions 
over accurate adjustment in fewer direc- 
tions is to be found in a comparison be- 
tween the higher parts of the nervous 
system in insects and birds. The insect 
performs its various actions instinctively 
and perfectly from the first. It is almost 
incapable of education and of modifying its 
actions as the result of the observation of 
SCIENCE. 
[N. 8. Von. VI. No. 146. 
the effects of some new danger. It would 
appear that the introduction of the electric 
light can only affect the insects which are 
most attracted to it, by the gradual opera- 
tion of natural selection. In the clothes- 
moths, which infest our houses, we may see 
an example of this; for these insects seem 
to be comparatively indifferent to light. 
Birds, on the other hand, have the power of 
learning from experience, of reasoning from 
the results of observation. At first terrified 
by railway trains, they learn that they are 
not dangerous, and cease to be alarmed ; 
while the effect of fire-arms results in their 
increased wariness. 
If this view of individual adaptability as 
due to natural selection be not accepted, it: 
may be supposed that the individual modi- 
fications are due either to the direct action 
of the external forces or to the tendencies 
of the organism. But it is impossible to. 
understand how the mechanical operation 
of such forces as pressure, friction, stress,. 
ete., continued through a lifetime, could 
evoke useful responses, or why the response 
should just attain and then be arrested at 
a level of maximum efficiency. The other 
supposition, that organisms are so consti- 
tuted that they must react under external 
stimuli by the production of new, useful 
characters, or the useful modification of old 
ones, seems to me to be essentially the same: 
as the old ‘innate tendency toward perfec- 
tion’ as the motive cause of evolution—a. 
conception which is not much more satis- 
factory than special creation itself. The 
inadequacy of these views is clearly shown 
when we consider that the external forces. 
which awake response in an organism gen- 
erally belong to its inorganic (physical or 
chemical) environment, while the useful- 
ness of the response has relation to its 
organic environment (enemies, prey, etc.). 
Thus one set of forces supply the stimuli 
which evoke a response to another and very 
different set of forces. We can, therefore 
