_Evolution is continuity, causal relation, gradual becoming_ --Increasing acceptance of this idea--First accepted for inorganic forms, mountains, continents and seas, rocks and soils, earth as a whole, heavenly bodies--Therefore acknowledged for all inorganics--Influence of geology in bringing about this change--Organic forms: acknowledged for individuals, true for classes, orders, families, genera --Races and varieties also formed gradually--Artificial species formed gradually--Examples of gradual changes in wild species--Hyatt’s researches--Other examples--Summing up of general evidence--Sufficient ground for induction-- But evolution is not only inductively probable but certain, axiomatic--It is the law of causation applied to forms, and therefore a necessary truth 53 CHAPTER II. SPECIAL PROOFS OF EVOLUTION. _Introductory._ _Special proofs necessary_--Evolution, though certain, is not yet accepted by the popular mind--Different departments from which proofs are drawn 67 _Origin of new organic forms; the old view briefly stated_-- Necessary to give a brief statement of theories--Old view-- Permanency of specific types--Supernatural origin of species --Centers of creation--Explanation of facts of geographical distribution--Of geological distribution--Modification of extreme view--Variability, but within limits--Illustrated 68 _The new view briefly stated_--Indefinite variability of organic forms--Effect of environment on rigid forms--On plastic forms--Taxonomic groups represent degrees of kinship 72 _Factors of evolution_--(1) Physical environment--(2) Use and disuse of organs--(3) Natural selection--(4) Sexual selection--(5) Physiological selection--Its necessity shown --Its operation explained--Compared with natural selection --Cause of variation unknown--Explanation of this is the next great step in the theory of evolution 73 CHAPTER III. THE GRADES OF THE FACTORS OF EVOLUTION AND THE ORDER OF THEIR APPEARANCE. _Factors of evolution restated; their grades and the order of their introduction shown_--Lamarckian factors, first in order because they precede sexual reproduction--(1) Environment--(2) Use and disuse--With sexual reproduction selective factors introduced--(3) Natural selection--(4) Physiological selection--(5) Sexual selection--With man was introduced (6) the rational factor--In this process two striking stages--viz., the introduction of sex and the introduction of reason--Effect of each to hasten the steps of evolution--The last by far the greater change 81