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 prevailing 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.