The unsophisticated man believes that all other animals exist to minister to his welfare; and from this point of view their adaptations are thought of solely in their relation to himself. A step in advance was taken when the idea was conceived that adaptations are for the good of the organisms themselves. It seemed a further advance when the conclusion was reached that the _origin_ of adaptations could be accounted for, as the result of the benefit that they conferred on their possessor. This view was the outcome of the acceptation of the theory of evolution, combined with Darwin’s theory of natural selection. It is the view held by most biologists at the present time; but I venture to prophesy that if any one will undertake to question modern zoologists and botanists concerning their relation to the Darwinian theory, he will find that, while professing _in a general way_ to hold this theory, most biologists have many reservations and doubts, which they either keep to themselves or, at any rate, do not allow to interfere either with their teaching of the Darwinian doctrine or with the applications that they may make of it in their writings. The claim of the opponents of the theory that Darwinism has become a dogma contains more truth than the nominal followers of this school find pleasant to hear; but let us not, therefore, too hastily conclude that Darwin’s theory is without value in relation to one side of the problem of adaptation; for, while we can profitably reject, as I believe, much of the theory of natural selection, and more especially the idea that adaptations have arisen because of their usefulness, yet the fact that living things must be adapted more or less well to their environment in order to remain in existence may, after all, account for the widespread _occurrence_ of adaptation in animals and plants. It is this point of view that will be developed in the following pages.