452 KINSHIP AND ADAPTATION 
as for instance the so-called rudimentary ovules of clematis, 
may escape entire obliteration. Characters of this sort are 
termed vestigial. Both vestigial and correlated characters 
imply adaptations—the one past and the other present—and 
thus may be said to result indirectly from natural selection; 
while even the acquired characters permitted by natural 
selection are most likely to survive when adaptational. Hence 
we may conclude that the central idea of Darwinism is the 
gradual accumulation through inheritance of slight selected 
adaptations. 
168. Acquirement versus selection. We have seen that 
the chief difficulty which the Lamarckians have to face 
comes from their unproved assumption that acquired charac- 
ters may be fixed by inheritance. The Darwinians on the 
other hand in their efforts to avoid this difficulty have fallen 
into others which we must now examine. Darwin tells us 
that he made it a rule to note down every fact or criticism 
adverse to his theory as soon as it came to his attention; for, 
as he shrewdly observes, what is unfavorable to one’s view 
is most likely to be forgotten. With the utmost candor he 
discussed in his writings every objection known to him. He 
was thus his own severest critic, and since he pointed out 
to his opponents their most effective lines of attack, there 
rightly belongs to him a share in whatever victories they 
gain in the cause of truth against his theory. Surely no one 
would rejoice more genuinely than he in any better explana- 
tion of the workings of evolution. 
Since natural selection operates only through adaptive 
variations we should expect that the various systematic 
groups of plants and animals, representing as they do the 
surviving branches of the evolutionary tree, would be very 
generally definable by adaptive characters or at least by 
characters which clearly imply adaptations past or present. 
But on the contrary it is just this sort of character which is 
found to have least systematic value, and therefore as a 
rule we find systematic groups most clearly defined by pe- 
culiarities which so far as we can tell have no relation what- 
ever to the vital needs of the organisms possessing them. In 
tracing the supposed evolution of clematis we chose a few 
