AvuGUST I, I912| 
The foliowing is the presidential address, de- 
livered by Major Leonard Darwin :— 
Thoughts suggestive of the general principle of 
evolution have been in the minds of many sages 
for many centuries. Not only have labourers in this 
field been found in all countries, but this great problem 
has been attacked from many different sides. Des- 
cartes and Leibnitz advanced from the basis of the 
physical sciences; Harvey viewed it as a physiologist ; 
Kant and Spencer as philosophers; Goethe as a poet, 
and Lamarck and Darwin as naturalists, or in that 
field of science where our present beliefs were most 
recently accepted. And the result of this long struggle 
for mental victory on the part of these and other 
great men was unquestionably the practically universal 
acceptance of the principle of evolution in all fields 
of knowledge in the ‘nineteenth century. For this 
great international achievement that epoch will ever 
remain famous. 
And what is this belief which is now so wide- 
spread? It is indeed one which is so simple and now 
so interwoven with all our thoughts that we are apt alto- 
gether to overlook its existence. A belief in evolution 
merely implies a belief that all changes which have taken 
place and which are taking place in this world are 
changes in which effects follow causes in accordance 
with unvarying laws. It is one of the consequences 
of our belief in this principle, rather than an example 
of the belief itself, that we regard the earth as we 
now see it—the rocks, hills, and valleys—as having 
been produced by the action through long ages of 
those same natural forces which we can still 
see and study in operation to-day; a field 
of science in which Lyell was the _ great 
evolutionary pioneer. As regards living beings, the 
belief that a knowledge of the changes going on before 
our eyes gives the key to what has taken place in 
the past has in like manner led to the general accept- 
ance of the view that all animals and plants are the 
descendants of some primitive form or forms from 
which they have been produced by some slow process 
of change. And this is indeed what the public now 
generally mean by evolution; although its essential 
feature is in reality to be found in the creed that all 
objects, animate and inanimate, are subject to the 
reign of natural law. Savages when they hear 
thunder hold that it is due to the fortuitous interven- 
tion of the thunder god; and when we, on the other 
hand, connect it with the generation in the air of 
electricity by friction or other natural processes, we 
are, in fact, asserting our belief in this underlying 
principle. And such a belief we now unhesitatingly 
avow whatever may be our creeds concerning the 
ultimate governance of the universe. Certainly it is 
in this spirit that all questions of fact in every field 
of science are now being investigated, and this is what 
is meant by the general acceptance of the principle 
of evolution. 
But if the essential idea of this principle is indeed 
so simple, wherein, it may be asked, does its import- 
ance lie? The great value of the belief that similar 
effects always follow similar causes lies in the fact 
that we are thus stimulated to endeavour to under- 
stand what has taken place in the past, and that the 
knowledge thus acquired gives us some power of look- 
ing into the future. Daily forecasts of the weather 
are now issued, and these forecasts will Gbviously be- 
come more and more trustworthy as our knowledge of 
the natural laws affecting the air and the skies become 
more and more perfect. If we had remained faithful 
to the creed of the savage as to the incalculable nature 
of storms, we should now have no faith in these fore- 
casts; or, in other words, without a belief in evolu- 
tion, meteorologists would never have been stimulated 
NO. 2231, VOL. 89] 
NATURE 
O09 
| to male those scientific researches which have already 
so greatly increased our prophetic powers. And our 
present scientific creed is unquestionably acting in a 
similar way as regards the study of man and his 
social progress. Indeed, it now seems obvious that 
in a changing world our powers of foretelling the 
future—that is of making any forecast concerning the 
results of the forces now at work—must entirely 
depend on our knowledge of the sequence of events 
in the past. It is for this reason that we are attach- 
ing greater and greater importance to the study of 
the natural laws regulating the sequence of human 
events; for without any such knowledge we should in 
this world be marching blindfold into an unknown 
future. And it will in time be recognised that it is 
by increasing our prophetic powers that a belief in 
evolution has conferred its greatest benefits on 
mankind. 
In order to make our knowledge of the evolutionary 
process practically useful, it is, therefore, obviously of 
the first importance that we should know how and 
why succeeding generations of mankind have re- 
sembled or differed from each other. The questions 
thus suggested for consideration may be divided under 
two main headings. In the first place it is to be 
noted that individually we pass on our learning and 
our thoughts to our juniors and our successors by 
writing and by word of mouth, whilst the material 
wealth of the nation in the form of improved sur- 
roundings is in a perpetual state of transference as 
time goes on. In other words, the environment of 
one generation is very largely dependent on the en- 
vironment of the generations which preceded it; and 
according as we are increasing or dissipating the mass 
of accumulated knowledge, as we are careful or care- 
less in the expression of our thoughts, as we add to 
or diminish the wealth of the nation, so is our con- 
duct tending to make the world progressive or retro- 
grade in this respect. No one can deny the import- 
ance of external conditions to the morals, health and 
comfort of mankind; and our instincts, selfish and 
unselfish, may be trusted to ensure a large amount of 
attention being always devoted to the factor of en- 
vironment in the evolutionary process. 
There is, however, on the other hand, another 
method by which each generation receives a heritage 
from its predecessors, and to which an adequate share 
of human thought has never as yet been given. With 
every increase in our scientific knowledge of the laws 
of life it becomes increasingly evident that the inborn 
qualities of the child are derived from its ancestors 
in accordance with laws which, though now but im- 
perfectly known, are gradually but surely being 
brought to light. If the future is thus tied to the 
past in accordance with these laws of heredity, we 
must be entirely dependent on our knowledge con- 
cerning them when endeavouring to ascertain whether 
the inherent qualities of the individuals composing 
the coming generations will show an improvement 
or the reverse in comparison with our standards of 
to-day; and, when thus peering into the future, it is 
therefore evident that a mere study of the factors 
directly and immediately affecting our present environ- 
ment, however important it may be, is wholly in- 
sufficient for our needs. There are, in fact, two great 
factors influencing us all through our lives, heredity 
and environment; and if at this congress we are 
chiefly concerned with the former—that is with nature 
rather than with nurture—it must not be assumed 
that little importance is attached by us to the many 
endeavours now being made to improve the environ- 
ment of the people, an object unquestionably greatly 
worth striving for. If we choose natural inheritance 
as the field for our operations, it is partly because it 
is not wise to attempt to cover too much ground on 
