WITH DARWIN FORWARDS 227 
variation, the correlation of variations, the occur- 
rence of unit characters, the brusqueness of muta- 
tions, and so on. There is a growing body of 
evidence, ¢.g., as regards chromosomes, that a 
variation is often a much more definite change 
than was formerly supposed, and the element of the 
casual or fortuitous seems to be reduced by the 
limitation that the new departure must be in some 
measure congruent with the germinal organization 
already established. It is not a “ guiding principle ” 
we assume, but simply the unity or individuality of 
the organism, as real when it is telescoped down 
into a germ-cell as when it finds epiphany in the 
full-grown creature. 
Tending also to a shrinkage of the apparently 
fortuitous is the fact, which Darwin clearly realized, 
that the sifting process often operates in reference 
to an intricate web of life, so that a nuance—a 
shibboleth—may have survival value; that natural 
selection operates, generally speaking, in relation 
-to an external systema Nature which has been in- 
creasingly elaborated through the ages, which is 
indeed part of the explanation of the progressiveness 
of evolution. There has been an evolution of the 
sieves as well as of the sifted. This idea is of 
far-reaching importance in relation to mankind, 
where so much of progress is registered outside 
protoplasm altogether in organizations and institu- 
tions, permanent products and cities, literature and 
art, the whole forming a vast sifting apparatus 
which is itself subject in detail to critical selection 
