MODERN CONCEPTIONS OF THE UNIVERSE. 7. 
Darwin endeavoured to account for the observed differences 
between forms which were supposed to be related as descendants 
and ancestors by the action of a kind of selection, operating upon 
the small variations to which each species is liable. He supposed 
that “ there will be a strong tendency for those individuals which 
show slight modifications in the direction of a better adaptation 
to their environment to survive at the expense of those of their 
brethren which do not exhibit similar modifications. This was 
the principle called “Natural Selection” by Darwin, and by 
Herbert Spencer the “Survival of the Fittest.” It was further 
supposed that under the influence of natural selection the small 
differences might in a sufficient time be accumulated and 
increased to almost any extent. Darwin* did not deny that 
many and serious objections might be advanced against his 
theory, out he thought that he had given them their full force. 
Of his theory he says, “nothing at first can appear more 
difficult to believe than that the more complex organs and 
instincts should have been perfected, not by means superior 
to, though analogous with, human reason, but by the accumula- 
tion of innumerable slight variations, each good for the 
individual possessor.” In spite of this difficulty, “ this suggestion 
of a natural means of modification had, within a few years, the 
effect of convincing practically the whole thinking world of the 
truth of the theory of organic evolution.” 
Darwin himself endeavoured to consider how far biological 
facts were in accordance with his theory, but “the more popular 
accounts since his time have dealt almost exclusively with theo- 
retical considerations and with matters of opinion.” Mr. R. H. 
Lock remarks that “if the truth must be told, the experimental 
method was given up for a long time by the majority of 
specialists themselves in favour of the controversial.” 
Of recent years there has been a return to experiment. The 
phenomena of variation and inheritance have been studied, and 
the result has emerged that improved features are not evolved 
by gradual selection. The theory of modification by selection 
has, when put to the test of experiment, very largely if not 
completely, failed. 
The place of selection has been taken by an alternative 
process. “The evidence in favour of an alternative process has 
multiplied even faster than the evidence against the continuous 
accumulation of minute differences.” “‘The new view is that 
the evolution of new species has taken place principally by the 
* Origin of Species, chapter xiv. 
