[Illustration: HEX CURASSOW FEEDING YOUNG BIRD, WITH PLUMAGE OF THE GLOBOSE CURASSOW] THE MAKING OF SPECIES BY DOUGLAS DEWAR, B.A. (Cantab), I.C.S., F.Z.S. AND FRANK FINN, B.A. (Oxon), F.Z.S., M.B.O.U. WITH FIFTEEN ILLUSTRATIONS LONDON: JOHN LANE THE BODLEY HEAD NEW YORK: JOHN LANE COMPANY MCMIX _Turnbull & Spears, Printers, Edinburgh_ PREFACE Post-Darwinian books on evolution fall naturally into four classes. I. Those which preach Wallaceism, as, for example, Wallace’s _Darwinism_, Poulton’s _Essays on Evolution_, and the voluminous works of Weismann. II. Those advocating Lamarckism. Cope’s _Factors of Evolution_ and the writings of Haeckel belong to this class. III. The writings of De Vries, forming a group by themselves. They advocate the theory that species spring suddenly into being; that new species arise by mutations from pre-existing species. IV. The large number of books of a more judicial nature, books written by men who decline to subscribe to any of the above three creeds. Excellent examples of such works are Kellog’s _Darwinism To-Day_, Lock’s _Recent Progress in the Study of Variation, Heredity, and Evolution_, and T. H. Morgan’s _Evolution and Adaptation_. All four classes are characterised by defects. Books of the two first classes exhibit the faults of ardent partisanship. They formulate creeds, and, as Huxley truly remarked, “Science commits suicide when it adopts a creed.” The books which come under the third category have the defects of extreme youth. De Vries has discovered a new principle, and it is but natural that he should exaggerate its importance, and see in it more than it contains. But, as time wears on, these faults will disappear, and the theory of mutations will assume its true form and fall into its proper place, which is somewhere between the dustbin, to which Wallaceians would relegate it, and the exalted pinnacle on to which De Vries would elevate it. In the present state of our knowledge, books of Class IV. are the most useful to the student, since they are unbiassed, and contain a judicial summing-up of the evidence for and against the various evolutionary theories which now occupy the field. Their chief defect is that they are almost entirely destructive. They shatter the faith of the reader, but offer nothing in place of that which they have destroyed. T. H. Morgan’s _Evolution and Adaptation_, however, contains much constructive matter, and so is the most valuable work of this class in existence.