Under the Maples by John Burroughs

That Darwin was a great natural philosopher and a good and wise man admits of no question, but to us, at this distance, it seems strange enough that he should have thought that he had hit upon the key to the origin of species in the slow and insensible changes which he fancied species underwent during the course of the geologic ages, and should thus have used the phrase as the title of his book. Had he called his work the "Variability of Species," or the "Modification of Species," it would not have been such a misnomer. Sudden mutations give us new varieties, but not new species. In fact, of the origin of species we know absolutely nothing, no more than we do about the origin of life itself.

Of the development of species we know some of the factors that play a part, as the influence of environment, the struggle for existence, and the competitions of life. But do we not have to assume an inherent tendency to development, an original impulse as the key to evolution? Accidental conditions and circumstances modify, but do not originate species. The fortuitous plays a part in retarding or hastening a species, and in its extinction, but not in its origin. The record of the rocks reveals to us the relation of species, and their succession in geologic time, but gives no hint of their origin.