606 Willis. — The Origin of Species by Large , rather than by 
1 ancestral ’ their common ancestor may be, we obtain a simple and satisfy¬ 
ing explanation. The present existing complex assortment of species 
must be conceived as having been evolved from a preceding and probably 
simpler one. 
So obvious an explanation was evolution that it had already been put 
forward in very early times, but no one had been able to suggest any way 
in which it might be supposed to produce its results ; and without a feasible 
mechanism no one was ready to accept it as an explanation, for it was not 
realized that its acceptance would make any difference to the progress 
of science. 
At this stage Charles Darwin came upon the scene as the man of the 
moment, putting forward the simple mechanism of Natural Selection, a 
principle which when once stated was seen to be of axiomatic nature, and 
a principle which caught, and has held, the public fancy. 1 It seemed clear 
that results might be produced by aid of this mechanism, and upon this 
ground evolution was rapidly accepted, for at that time the laws of heredity 
were not understood, and it was supposed that all change, due to whatever 
kind of variation, fluctuating or not, was fully inherited, a supposition that 
later work has shown to be ill-founded. 
Evolution, once adopted, was found to explain so enormous a range of 
facts, and its acceptance pointed the way to so many new lines of research, 
that it rapidly attained an unassailable position, quite independent of any 
support that might be given to it by the theory of Natural Selection. For 
a long period, however, Evolution and Natural Selection were not sharply 
distinguished from one another, and anything that gave evidence in support 
of the former was also supposed to uphold the latter, though the inherent 
logical weakness of this position was often pointed out. For a long time the 
current of opinion in favour of ‘ Darwinism ’ was too strong to take account 
of any obstacles. I have lately looked over some anti-Darwinian books in 
the Cambridge University Library, and have been struck with the frequency 
of such observations as the following : 
‘ It follows, therefore, that if we accept the Evolutionists’ view, every 
specialised chemical compound met with in some living beings only must 
fulfil the condition, that every approximation to the complete compound 2 
must have been of advantage to the being in which it was produced in the 
struggle for life . . . unless these very substances existed in, and formed points 
of difference between, Mr. Darwin’s few original forms’ ( 9 , p. 134). 
Small steps in the production of chlorophyll, for example, could not be 
of any advantage ( 9 , p. 168). On p. 188 Maclaren asks why a plant should 
1 Because, it has been suggested to me by Mrs. Arber, each man is pleased to think that he is 
one of those picked out by selection. 
2 A thing which does not occur in nature, it is pointed out. 
