SEPTEMBER 14, 1899] 
NALURE 
467 
ivory balls carved by Chinese hands, one within the other. 
This was no fantastic view put forward by an imaginative 
dreamer ; it was seriously held by sober men, even by men like’ 
yi y 
the illustrious Haller, in spite of their recognising that as the 
chick grew in the egg some changes of form took place. 
Though so early as the middle of the eighteenth century 
Friedrich Caspar Wolff and, later on, others had strenuously 
opposed such a view, it held its own, not only to the close of the 
century, but far on into the next. It was not until a quarter of 
the present century had been added to the past that Von Baer 
made known the results of researches which once and for all 
swept away the old view. He and others working after him 
made it clear that each individual puts on its final form and 
structure, not by an unfolding of pre-existing hidden features, 
but by the formation of new parts through the continued 
differentiation of a primitively simple material. It was also 
made clear that the successive changes which the embryo 
undergoes in its progress from the ovum to maturity are the ex- 
pression of morphologic laws, that the progress is one from the 
general to the special, and that the shifting scenes of embryonic 
life are hints and tokens of lives lived by ancestors in times 
long past. 
If we wish to measure how far off in biologic thought the end 
of the last century stands, not only from the end but even from 
the middle of this one, we may imagine Darwin striving to 
write the ‘Origin of Species” in 1799. We may fancy 
him being told by philosophers that one group of living 
beings differed from another group because all its members 
and all their ancestors came into existence at one stroke when 
the firstborn progenitor of the race, within which all the rest 
were folded up, stood forth as the result of a creative act. . We 
may fancy him listening to a debate between the philosopher 
who maintained that all the fossils strewn in the earth were the 
remains of animals or plants churned up in the turmoil of a 
violent universal flood, and dropped in their places as the waters 
went away, and him who argued that such were not really the 
“spoils of living creatures,” but the products of some playful 
plastic power which out of the superabundance of its energy 
fashioned here and there the lifeless earth into forms which 
imitated, but only imitated, those of living things. Could he 
amid such surroundings by any flight of genius have beat his 
way to the conception for which his name will ever be known ? 
Here I may well turn away from the past. It isnot my 
purpose, nor, as I have said, am I fitted, nor is this perhaps the 
place, to tell even in outline the tale of the work of science in 
the nineteenth century. I am content to have pointed out that 
the two great sciences of chemistry and geology took their birth, 
or at least began to stand alone, at the close of the last century, 
and have grown to be what we know them now within about a 
hundred years, and that the study of living beings has within 
the same time been so transformed as to be to-day something 
wholly different from what it was in1799. And, indeed, to say 
more would be to repeat almost the same story about other 
things. If our present knowledge of electricity is essentially 
the child of the nineteenth century, so also is our present know- 
ledge of many other branches of physics. And those most 
ancient forms of exact knowledge, the knowledge of numbers 
and of the heavens, whose beginning is lost in the remote past, 
have, with all other kinds of natural knowledge, moved onward 
during the whole of the hundred years with a speed which is 
ever increasing. I have said, I trust, enough to justify the 
statement that in respect to natural knowledge a great gulf lies 
between 1799 and 1899. That gulf, moreover, is a twofold 
one: not only has natural knowledge been increased, but men 
have run to and fro spreading it as they go. Not only have the 
few driven far back round the full circle of natural knowledge 
the dark clouds of the unknown which wrap us all about, but 
also the many walk in the zone of light thus increasingly gained. 
If it be true that the few to-day are, in respect to natural know- 
ledge, far removed from the few of those days, it is also true 
that nearly all which the few alone knew then, and much which 
they did not know, has now become the common knowledge of 
the many. 
What, however, I may venture to insist upon here is that the 
difference in respect to natural knowledge, whatever be the case 
with other differences between then and now, is undoubtedly a 
difference which means progress. The span between the science 
of that time and the science of to-day is beyond all question a 
great stride onwards. 
NO. 1559, VOL. 60] 
We may say this, but we must say it without boasting. For 
the very story of the past which tells of the triumphs of science 
bids the man of science put away from him all thoughts of vain- 
glory. And that by many tokens. f 
Whoever, working at any scientific problem, has occasion to 
study the inquiries into the same problem made by some fellow- 
worker in the years long gone by, comes away from that study 
humbled by one or other of two different thoughts. On the 
one hand, he may find, when he has translated the language of 
the past into the phraseology of to-day, how near was his fore- 
runner of old to the conception which he thought, with pride, 
was all his own, not only so true but so new. On the other 
hand, if the ideas of the investigator of old, viewed in the light 
of modern knowledge, are found to be so wide of the mark as 
to seem absurd, the smile which begins to play upon the lips 
of the modern is checked by the thought, Will the ideas which 
I am now putting forth, and which I think explain so clearly, 
so fully, the problem in hand, seem to some worker in the far 
future as wrong and as fantastic as do these of my forerunner to 
me? In either case his personal pride is checked. Further, 
there is written clearly on each page of the history of science, in 
characters which cannot be overlooked, the lesson that no 
scientific truth is born anew, coming by itself and of itself. Each 
new truth is always the offspring of something which has gone 
before, becoming in turn the parent of something coming after. 
In this aspect the man of science is unlike, or seems to be 
unlike, the poet and the artist. The poet is born, not made ; 
he rises up, no man knowing his beginnings; when he goes 
away, though men after him may sing his songs for centuries, he 
himself goes away wholly, having taken with him his mantle, 
for this he can give to none other. The man of science is not 
thus creative ; he is created. His work, however great it be, 
is not wholly his own; it is in part the outcome of the work of 
men who have gone before. Again and again a conception 
which has made a name great has come, not so much by the man’s 
own effort as out of the fulness of time. Again and again we 
may read in the words of some man of old the outlines of an 
idea which in later days has shone forth as a great acknowledged 
truth. From the mouth of the man of old the idea dropped 
barren, fruitless ; the world was not ready for it, and heeded it 
not ; the concomitants and abutting truths which could give it 
power to work were wanting. Coming back again in later 
days, the same idea found the world awaiting it ; things were in 
travail preparing for it ; and some one, seizing the right moment 
to put it forth again, leapt into fame. It is not so much the 
men of science who make science, as some spirit which, born of 
the truths already won, drives the man of science onward, and 
uses him to win new truths in turn. 
It is because each man of science is not his own master, but 
one of many obedient servants of an impulse which was at work 
long before him, and will work long after him, that in science 
there is no falling back. In respect to other things there may be 
times of darkness and times of light, there may be risings, de- 
cadences, and revivals. In science there is only progress. The 
path may not be always a straight line, there may be swerving to 
this side and to that, ideas may seem to return again and again 
to the same point of the intellectual compass ; but it will always 
be found that they have reached a higher level—they have 
moved, not in a circle, but in a spiral. Moreover, science 1s 
not fashioned as is a house, by putting brick to brick, that which 
is once put remaining as it was put to the end. The growth of 
science is that of a living being. As in the embryo phase 
follows phase, and each member of the body puts on in suc- 
cession different appearances, though all the while the same 
member, so a scientific conception of one age seems to differ 
from that of a following age, though it is the same one in the pro- 
cess of being made; and as the dim outlines of the early embryo, 
as the being grows, become more distinct and sharp, like a pic- 
ture on ascreen brought more and more into focus, so the dim 
gropings and searchings of the men of science of old are by 
repeated approximations wrought into the clear and exact con- 
clusions of later times. 
The story of natural knowledge, af science, in the nineteenth 
century, as, indeed, in preceding centuries, is, I repeat, a story 
of continued progress. There is in it not so much as a hint 
of falling back, not even of standing still. What is gained 
by scientific inquiry is gained for ever; it may be added to, 
it may seem to be covered up, but it can never be taken away. 
Confident that the progress will go on, we cannot help peering 
