To begin with the _Biological_. This is briefly stated by Bishop Temple {7a} in the words: “It cannot be denied that Darwin’s investigations have made it extremely probable that the vast variety of plants and animals have sprung from a much smaller number of original forms.” So Darwin, in his summary, {7b} writes: “The several classes of facts which have been considered in this chapter seem to me to proclaim so plainly that the innumerable species, genera, and families with which this world is peopled, are all descended, each within its own class or group, from common parents, and have all been modified in the course of descent, that I should without hesitation adopt this view, even if it were unsupported by other facts or arguments.” I presume that there are very few amongst us who would differ materially from either of these statements; for both of them fully admit the original existence of a variety of common parents, which is, in fact, a complete surrender of the whole position; and Darwin limits the modifications in the course of descent to changes, “each within its own class or group.” Now this is all for which the anti-evolutionist contends; for all admit most freely the existence of most marked variations within the circles of the various groups. But, although in this passage there is this limitation, as a matter of fact there is a great deal more claimed by both writers for Evolution; for the title of Darwin’s book, “The Origin of Species,” shows very clearly that he applies his theory not merely to variations within species, but to the formation of the species within which these variations take place. I do not gather from his book that his theory goes so far as to suppose that either plants or animals have passed over from one species to another, both species being already in existence; but rather that through the power of “the struggle for existence,” “natural selection,” and “survival of the fittest,” existing races have been so changed and modified that new species have been evolved out of them, and that in every such evolution there has been what evolutionists consider to be improvement. The arguments which Bishop Temple adduces for this theory are— (1) “The unity of plan which can be found pervading any great class of animals seems to point to unity of ancestry.” {7c} He illustrates this by remarking that vertebrate animals are formed on a common plan. (2) “Slight variations are perpetually being produced.” {7d} (3) “The frequent occurrence both in plants or animals of useless parts which still remain as indications of organs that once were useful, and have long become useless.” {7e}