1020 LIFE : OUTLINES OF GENERAL BIOLOGY 



final result. Thus the eye was primarily a light-and-shade organ, 

 not for image-forming; and the ear was for^agesj^an equilibrating 

 organ before it had become a hearing ear. 



And as we re-read Darwin we cannot but appreciate his extra- 

 ordinary realisation of the subtlety of Natural Selection, a subtlety 

 of which, in his humility, he said that he did not always find it 

 easy to keep it in mind. Nature's sifting operates in relation to a 

 very intricate web of life ; her winnowing may detect a nuance ; an 

 organism that says Shibboleth may have survival value as against 

 one that says Sibboleth. 



Yet when it is asked how the System of Animate Nature 

 has come to be, the answer is frankly that we require Brahma 

 the creator as weU as Kali the destroyer. Darwin postulated the 

 Proteus, admitting that its quick changes were beyond him. 



Fig. 178. 

 Two Variations (A and B) in the Foliage of the Same Species of Geranium. 



"What the devil", he said, "determines each particular variation?" 

 Thanks to Bateson, De Vries, and many others, we know much 

 more about variations than Darwin did; thanks to Mendel, 

 and Weismann, and many others, we know much more about the 

 laws of their entailment than Darwin did; but we are mostly 

 lagging seriously behind Darwin in the development of the doctrine 

 of Selection. "Evolution", as Graham Kerr recently said, "is a 

 philosophy of wild nature"; and it is when we envisage organisms 

 in their natural surroundings that we realise the evolution of sieves 

 as well as the evolution of the material to be sifted. Linkages 

 established in the System of Nature operate on the whole against 

 retrogression and towards advance. No doubt the tapeworm is the 

 outcome of evolution as well as the Golden Eagle, for fitness is rela- 

 tive to the particular conditions of each life; yet on the whole the 

 emergence of the Golden Eagle is more typical of the evolutionary 

 process, which is integrative at the core. We do not doubt that 

 Natural Selection sometimes puts on a brake, even on variability; 



