I'oulton.l 372 [Mayi6, 
as capable of being made only in the laboratory of the living 
body. Many of these can now certainly be produced, but that is 
very different indeed from creating protoplasm endowed with life ; 
and so far are we from acliieving this by any chemical means, that 
I think we may venture to dismiss all consideration of the ulti- 
mate origin of life. 
But granting the origin of living matter, these theories of evo- 
lution which we are considering and hope to discuss to-night can 
deal with it, and with then- help we believe that we c:in account 
for what has subsequently happened ; namely, the evolution of all 
forms of life, animal and vegetable, upon the surface of the earth. 
The first of these theories which I propose to discuss is the 
well-known Darwin- Wallace theory of natural selection, with its 
three factors. 
First, individual variation, — the fact that individuals differ, 
and that the differences are essential or inherent in the organism, 
so that even if animals were brought up alike, we know they 
would still be unlike, and so that, however much the offspring 
may resemble their parents, they are never exactly like their 
parents or exactly like each other. There is, then, first, indi- 
vidual difference, one of the most essential facts in the organism. 
Secondly, the fact of heredity, — the fact that these inherent 
differences may be and. are inherited. Although the hereditary 
transmission of acquired differences is disputed, the transmission 
of those that are inherent is certain. This stands before us as 
one of the most obvious and certain of conclusions, equally proved 
by the observation and experience of every one of us. 
Thirdly, the fact that there must be a struggle for existence ; 
that there are far more individuals born into the world in every 
species, even the most slowly increasing, than can possibly survive 
and reproduce. 
These three factors must by logical necessity lead to a survival 
of the fittest among individual variations. It does not require a 
scientific mind to comprehend that, — to infer that some amount 
of evolution must ensue from the co-operation of those three 
factors, every one of which stands firm and undisputed. Among 
all the advocates of rival' theories which have been brought 
forward to explain evolution, no one has ever ventured to attemi)t 
to disprove any one of these three factors. They stand unchal- 
lenged. 
