ing Darwin has been largely one of deductive science. The formulation of the law of natural selection started an immense amount of speculation as to how it might act and what it would produce under certain conditions. A very large part of the discussion is such as might be drawn directly from the law itself without any special appeal to nature for information. The younger naturalists are expressing themselves as dissatisfied with this method of study, insisting that if we are to advance any further in the subject it must be by inductive methods rather than deductive. We must leave our libraries and turn to nature to see what is actually going on, leave speculation and turn to observation. A new era in the evolution discussion is coming with new men. The younger naturalists are beginning to hunt in new fields rather than in those already well explored, and we may expect the aspect of the problem to be greatly changed as the result of this new attitude. The last fifteen years have seen a very profound modification of our ideas concerning the origin of species, but the facts that have produced the change have hardly been within the reach of the person who is interested in evolution but cannot follow the discussion in its various ramifications in scientific journals. The purpose of this work is to present to such students a review of the subject of evolution as it stands to-day, at the time when our younger naturalists are abandoning old methods and beginning to search in new fields for new information. One of the most significant fields of the application of evolutionary methods of study is that of mental phenomena, including the study of instinct and intelligence, together with the evolution of civilization. The limits of this work make it impossible to deal with this most important subject, which must, therefore, be reserved for a later work. MIDDLETOWN, August, 1899. NOTE.-Figures 8, 10, 11, and 13-24 are from the author's Story of the Living Machine, and have been loaned by D. Appleton & Co. حمق THE QUESTION OF METHOD. DARWIN'S SOLUTION. The answer given by Lamarck-The answer given by Darwin-Darwin's five links-Origin of an eye as an illustration of natural selection-Facts to be explained by natural selection: adaptation, divergence, discontinuity -Strength of the law of natural selection - Development Prodigality in nature-Struggle for existence; mankind, lower animals and plants-Struggle for the life of others -Survival of the fittest, or natural selection-Selection based on mean types - Natural selection - Utility- 13 ΙΟΙ Are variations continuous or discontinuous ?- Do dis- continuous variations originate new types?-Discontin- uous variations as explaining the beginnings of organs - Are variations determinate or hap-hazard? - Deter- PAGE Acquired and congenital variations-Weismann's theory of heredity-The essence of heredity - The essence of variation- Modifications of Weismann's original theory -Deductions from Weismann's theory - Effect of envi- ronment-Weismann's theory and principle of utility— Weismann's theory and the principle of disuse — Pan- METHOD OF EVOLUTION UNDER THE LIGHT OF Relation of Weismannism to the problems of variation and evolution-Weismannism both a theory of heredity and a theory of evolution - Stability of germ plasm, theoretical conclusions-Stability; evidence from obser- vations Instability as affecting evolution - Perpetual continuity of germ plasm; theoretical conclusions - heritance of acquired characters Weismann's theory - |