CHAPTER I.. Its Scope and Definition.

ITS SCOPE AND DEFINITION.

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A type of evolution--Development of an egg 3

Universality of evolution--Pervades all nature and concerns all departments of thought--One half of all science-- Illustrated (1) by human body, (2) by solar system, (3) by society, (4) by earth, (5) by organic kingdom--The term evolution usually, but not rightly, confined to this last 3

Definition of evolution--I. Progressive change--Shown in the animal body, or the Ontogenic series--In the animal scale, or the Taxonomic series--In the geological, or Phylogenic series--The three series similar, though not identical 8

II. Change according to certain laws--Three laws of succession of organic forms 11

(a) Law of differentiation--Early forms are generalized; afterwards separated into specialized forms--Illustrated by fishes, by birds--Whole process of differentiation illustrated by growth and branching of a tree 11

(b) Law of progress of the whole--Mistake of confounding evolution with upward progress--How far true, and how far false--Illustrated by branching tree--Examples of this mistake in the popular mind--In the scientific mind 13

(c) Law of cyclical movement--Shown in geological history-- Age of mollusks, fishes, reptiles, mammals, man--Illustrated again by a branching tree--Increasing complexity as well as height--Illustrated by diagram 16

The above three laws are laws of evolution--Differentiation --Shown in the development of an egg, the type of evolution 19

Progress of the whole--Not progress of all parts--Shown in the development of an egg 22

Cyclical movement--Less fundamental than other two--Shown in Ontogeny of body, of mind--Increasing complexity--Necessity of continued advance--Otherwise deterioration--All these laws shown in progress of society---Differentiation shown-- Progress of the whole but not of all parts shown--Cyclical movement shown--In social evolution, however, there is another element, viz., conscious voluntary progress---This kind of evolution contrasted with the other 22

III. Change by means of resident forces--This is the point of dispute--Sense in which we use term resident forces--Does not touch question of origin of natural forces 27

The two views of the origin of organic forms briefly contrasted --As to whether natural or supernatural--As to variability, definite or indefinite--As to change from one species to another by transmutation or substitution--As to universality of law of continuity 29