20 
But now, in the last place, we encounter 
in the recent writings of some of the ex- 
perimental morphologists a singular atti- 
tude of mind toward other methods of 
study and, in particular, toward the com- 
parative method and the historical point of 
view in biology generally, for it is seriously 
maintained that the scientific study of 
organic nature is possible through experi- 
ment and through experiment alone. That I 
am not overstating the case will be evident 
from the following citations from recent 
utterances by an eminent leader in this 
field. ‘‘ The comparative method in mor- 
phology,” he says, ‘‘ is in itself not science, 
but only a preparation for scientific work.” 
Speaking for the self-styled ‘rational mor- 
phologists’ he says, ‘We have not a 
method of scientific morphology, but the 
scientific morphological method. There is but 
one productive method, and that is our 
method.” The historical point of view in 
comparative morphology is of wholly minor 
value. Even could we accurately deter- 
mine the ancestral origin of plants and 
animals—which in point of fact we cannot 
do—we should still not have solved the real 
problem—namely, the laws in accordance 
with which evolution has taken place. 
The most complete acquaintance with phy- 
logeny would give us only an ancestral por- 
trait-gallery, nothing more than a ‘ photo- 
graph of the problem.’ Only through 
systematic experiment can we unveil the 
nature and limits of the power of trans- 
formation that lies at the root of the evolu- 
tionary process. 
We may as well admit forthwith that 
there is a large element of truth in this bold 
claim, and it is well to recall how promi- 
nent a place the experimental evidence of 
evolution held in Darwin’smind. The his- 
tory of science shows incontestably that 
only through experiment, through deliber- 
ately calculated and precise alterations in 
the conditions under which phenomena 
SCIENCE. 
[N. 8. Vou. XIII. No. 314. 
occur, can we attain the limits of scientific 
analysis. So long, therefore, as the natur- 
alist limits himself to the study of vital 
phenomena under natural conditions, he 
falls short of the highest ideal of scientific 
investigation. For my part, I am wholly 
ready to admit that the introduction of ex- 
perimental methods into morphology is the 
most momentous step in biological method 
that has been taken since the introduction 
of such methods into physiology by Harvey 
and Haller. As regards the comparative 
method, I do not overlook the force of the 
argument that when comprehensive con- 
clusions are attained by the mere elimina- 
tion of facts that are not common to all 
the individual cases compared, those con- 
clusions must have a more limited content 
than the collective data on which they are 
based, though I suspect that it would not 
require a very long search to discover a 
fallacy lurking here. But seriously to 
maintain that the non-experimental com- 
parative study of nature is not science is an 
efflorescence of enthusiasm at which one 
could hardly repress a smile did it not 
involve so serious a blunder. 
Now I certainly shall not undertake 
such a work of supererogation as a defense 
of the comparative method in natural his- 
tory. Moreover, the statements cited were, 
I believe, intended mainly as a protest 
against too free genealogical speculation, 
and perhaps conveyed more than their au- 
thor really intended. Yet the undoubted 
truth that they embody is masked by a 
form of expression so misleading, that even 
before this audience of naturalists I shall 
venture to place beside them the words 
of one or two of those best qualified to 
pass judgment on scientific method in the 
domain of physical science, which may 
rightly claim to be the experimental science 
par excellence. Helmholtz, in a discourse 
on the relation of natural science to gen- 
eral science, delivered at Heidelberg forty 
