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, e.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 progressivcness 

 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 



