CHAPTER I. THE DARWINIAN THEORY OF ORGANIC EVOLUTION. NOTWITHSTANDING the dissent of many eminent authorities, the theory of the Evolution of species by natural selection, made public by Darwin in 1859, still holds the field, and as a comparison of his theory with that in the preceding pages will tend to disclose their respective values, we now proceed to set forth Darwin's views as we gather them from his works, and to examine impartially, if possible, the evidence and arguments adduced in their support. It would be beyond the scope of this work to examine exhaustively all Darwin's writings on evolution, and we shall therefore deal only with the more important phenomena referred to by him, and his interpretation of their meaning. Darwin nowhere offers any views respecting the origin of life, nor does he formulate his theory, but, assuming the existence of life in its simplest forms, sets forth at great length the facts and arguments, which he says have thoroughly convinced him That all animals and plants have been evolved from a few progenitors, and possibly from one prototype only. That new species have been evolved principally by natural selection, acting through the struggle for existence; aided (a) to an important extent by the inherited effect of the use and disuse of parts, and (b) to an unimportant extent by the direct action of the external conditions of life. That small beneficial differences appeared from time to time in some members of a species, and, being accumulated by heredity through numberless successive generations, during vastly extended periods of time, ultimately became specific variations, and thus new species arose.1 The principal phenomena adduced in port of these conclusions are sup The similarity in structure and organisa tion of successive types. 1 See 'Origin of Species,' Ed. vi., p. 421. The differences among animals of admittedly the same race. The known effects of (a) selective breeding, (b) the use or disuse of parts, and (c) the direct action of external conditions of existence. We propose first to define what we mean by a "race," and then to examine in detail the real meaning and significance of the phenomena to which Darwin appeals, and also the value of the arguments based on his interpretation of these phenomena. |