I am fully aware of the danger in attempting to cover so wide a field as that of “Evolution and Adaptation,” and I cannot hope to escape the criticism that is certain to be directed against a specialist who ventures nowadays beyond the immediate field of his own researches; yet, in my own defence, I may state that the whole point of view underlying the position here taken is the immediate outcome of my work on regeneration. One of the general questions that I have always kept before me in my study of regenerative phenomena is how such a useful acquirement as the power to replace lost parts has arisen, and whether the Darwinian hypothesis is adequate to explain the result. The conclusion that I have reached is that the theory is entirely inadequate to account for the _origin_ of the power to regenerate; and it seemed to me, therefore, desirable to reëxamine the whole question of adaptation, for might it not prove true here, also, that the theory of natural selection was inapplicable? This was my starting-point. The results of my examination are given in the following pages. I am deeply indebted to Professor G. H. Parker and to Professor E. G. Conklin for advice and friendly criticism; and in connection with the revision of the proof I am under many obligations to Professor Joseph W. Warren and to Professor E. A. Andrews. Without their generous help I should scarcely have ventured into a field so full of pitfalls. Bryn Mawr, Penn., June 10, 1903. ------------------------------------------------------------------------ CONTENTS CHAPTER I PAGE The Problem of Adaptation 1 – Structural Adaptations 1 – Adaptations for the Good of the 19 Species – Organs of Little Use to the 22 Individual – Changes in the Organism that are 25 of No Use to the Individual or to the Race – Comparison with Inorganic 26 Phenomena CHAPTER II The Theory of Evolution 30 – Evidence in Favor of the 32 Transmutation Theory – – Evidence from Classification 32 and from Comparative Anatomy – – The Geological Evidence 39 – – Evidence from Direct 43 Observation and Experiment – – Modern Criticism of the Theory 44 of Evolution CHAPTER III