Stuart Phelps, now deceased, whose life and labor all those who had the privilege of sharing his instruction and benefiting by his kindness must ever hold in grateful remembrance. CONTENTS PART I PAGES INTRODUCTORY REMARKS 1-2 DARWIN 2-12 WALLACE 12-23 HAECKEL 23-28 SPENCER 28-76 FISKE 77-82 ROLPH 82-107 BARRATT 107-120 STEPHEN 120-143 CARNERI 143-175 HOeFFDING 175-200 GIZYCKI 200-224 ALEXANDER 225-263 (REE) 264-268 PART II INTRODUCTION Refutation of _a priori_ objections to Evolutional Ethics, and a statement of reasons for supposing that an application of the theory of Evolution to Ethics must be of use 269-276 CHAPTER I THE CONCEPTS OF EVOLUTION Extension of the meaning of Darwinian concepts since Darwin--Lewes on the Struggle for Existence as internal--The mystery of "Variation" according to Darwin not a metaphysical mystery, but one of the incompleteness of scientific knowledge--Rolph's criticism of the Darwinian conception of the Struggle for Existence criticised--General classification of the theories of Evolution--Fechner's theory of the Tendency to Stability--Petzoldt on Fechner--Petzoldt's concepts of Tendency and Competition--Zoellner and Du Prel--Examination of the concept of Absolute Stability, and of a full stability of the universe, in the light of the question as to the finite or infinite character of the material universe--Periodicity in Organisms--Criticism of the concepts of Cause and Effect--Criticism of Spencer's definition of Life--The concepts of Heredity and Adaptation--The point of dispute with regard to Variation--Darwin, Haeckel, and Eimer with regard to the inheritance of individual acquirements--Criticisms of Weismann--Habit in the life of the individual--Advantage of the method pursued by Avenarius in the "Kritik der reinen Erfahrung"--Lamarck on the relation of Use and Function--Darwin on Habit and Instinct--Function and Tendency to Function--Relation of organism and environment--Theory of a special vital force--The relation of exercise to strength of Tendency--The concepts of Cause and Effect as applied to organism and environment--Relation of primary tendency to later-evolved function--Form and Function--The mixture of types in sexual propagation--Summary of conclusions 277-306 CHAPTER II INTELLIGENCE AND "END"