JANUARY 4, 1901.] 
germ-layer theory, and your fin de siecle 
student merely remarks stolidly, as he reels 
off a yard or two of ribbon-sections from 
his Minot microtome, ‘‘ Of course not; but 
what is the use of talking about such an 
antediluvian myth?’ It isenough to make 
Balfour turn in his grave ! 
I do not propose to review the advance of 
discovery in recent years, but only to offer a 
few reflections on the progress of our aims, 
methods and standpoints, taking as my 
point of departure Louis Agassiz’s delight- 
ful little book, entitled ‘ Methods of Study 
in Natural History,’ publishedin1863. In 
this work we find a clear and simple expo- 
sition of the aims and methods of natural 
history as they appeared to a great natural- 
ist and teacher before the theory of evolution 
had wrought its wonderful transformation 
in natural science. We all know that, as 
far as that theory was concerned, Agassiz 
ranged himself on the side of a losing cause, 
believing, to quote his own words, that 
naturalists were chasing a phantom in their 
search after some material gradation among 
created beings such as that theory de- 
manded, though he was constrained to the 
admission that ‘this notion’ had a certain 
fascination forthe human mind. Jam here 
concerned with Agassiz’s position on this 
question only in its bearing on his aim and 
method. It was Agassiz’s aim, first, to ob- 
serve phenomena with all possible accuracy; 
and, second, to arrange and classify them 
in order to discover the ‘natural affinities’ 
of living things. His method, on the all- 
importance of which he was never weary 
of dwelling, was that of his master, Cuvier, 
comparison. “ The true method of obtaining 
independent knowledge”’ he says “‘ is this 
very method of Cuvier’s—comparison.”’ 
“«The education of a naturalist now consists 
chiefly in learning how to compare.”’ It 
was not Agassiz’s aim to analyze and ex- 
plain phenomena, as Darwin was attempting 
todo. His whole theory of organic creation 
SCIENCE. 
15 
precluded such an aim; for existing phe- 
nomena of life were viewed as the result, 
not of progressively operating causes, but 
of special creation, and ‘natural affinities ’” 
among living things were but the expres- 
sion of creative thought. It was enough 
for him to observe, compare and classify. In 
his work one is everywhere struck with the 
eager and enthusiastic delight that he took 
in the facts of natural history for their own 
‘sake. The key note of Agassiz’s work was, 
in short, the love of nature, and his remarkable 
success as a teacher was mainly due to his 
power of inspiring a like enthusiasm in 
others. Such, in few words, were what 
seem to me the characteristic features in 
Agassiz’3 aim and methods. They may 
have for us later naturalists a useful lesson, 
both in their agreement with, and their 
contrast to, some of the latest dicta of mod- 
ern writers on scientific method. 
Leaving aside for the moment the subject 
of experimental physiology, we may say 
broadly that the progress of natural history 
since Agassiz’s time has been along three 
general lines of study, though no very defi- 
nite line of demarkation between them can 
be drawn. First came the development of 
comparative morphology, dominated by 
Agassiz’s method of observation and com- 
parison, but largely inspired by a theory of 
organic forms that was the very antipode 
of hisown. Here belong the elaborate and 
exact modern investigations on general and 
systematic zoology and botany, on geo- 
graphical and geological distribution and 
on comparative anatomy and embryology. 
In all these, a leading motive was to search 
for natural affinities and to interpret them 
in accordance with the theory of evolution. 
It has been a laborious and persistent 
quest, carried forward on a vast scale ; and 
there is now hardly a corner of the plant or 
animal kingdom into which it has not been 
pressed. Its point of departure was pri- 
marily given by the comparative anatomy 
