Introduction 



There are collected in this volume some of the articles or 

 lectures I have written or delivered over the past ten years. 

 Most of them deal with problems of evolution, a choice which 

 may be thought to need a word of justification. Not so long ago 

 there was a slump in research and thought on evolution. 

 Darwin''s successors had made it their business to reveal and 

 expound the detailed progress of evolution, but did not feel 

 obliged to commit themselves to any particular theory of its 

 mechanism. Their work reached its peak with the publication 

 of the majestic but unfinished Treatise of Zoology^ under Ray 

 Lankester's editorship, shortly before the First World War; it 

 was founded squarely upon the concept of '"homology"', i.e. of 

 the evolutionary connections between parts of animals — 

 between fins and wings and limbs, for example — rather than 

 between animals considered as a whole. But between that 

 Augustan age of comparative anatomy and the rethinking of 

 Darwinism in the language of genetics, almost no progress was 

 made in the understanding of the evolutionary mechanism. 

 Many biologists became querulous and uneasy about the pre- 

 vailing Darwinian theory — a dissatisfaction nowhere to be 

 more clearly seen than in that great baroque masterpiece of 

 biological literature, D''Arcy Thompson'^s essay On Growth and 

 Form (1915). Laymen were therefore to be forgiven if they 

 thought that Darwinism had been discredited or had died of 

 inanition. The pity is that, in spite of the advocacy of two 

 generations of Huxleys, many educated laymen hold that 

 opinion still, although any good ground for doing so has long 

 since disappeared. 



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