varied structure where this in a predominant degree aids them in fulfilling the vital requirements of their lives.
Mark, now, how the strong contrast set forth in the preceding section is thus strengthened. We saw that the evolution-hypothesis is indirectly supported by five great classes of observed facts; and that the perpetual adaptation and re-adaptation of constitution to conditions is a general cause of the kind required to account for these facts. Here we see that, of the special causes which effect adaptation, the chief one, survival of the fittest, is not only one the operation of which we can clearly conceive, but one which it is impossible to conceive as not operating. On the other hand, we saw that there are absolutely no observed facts which yield indirect support to the hypothesis of special creation; but that, contrariwise, all the observed facts of daily experience, proving a constant order among phenomena, negative the hypothesis. And we also saw that while the process of special creation can not be rationally conceived, the negation of it is perfectly conceivable. Thus, bringing the contrast to a focus, it appears that the one is credited both a posteriori and a priori, and the other is discredited both a posteriori and a priori. No stronger contrast in credibility can well be imagined.
Authoritative expositions of the process of natural selection afford no basis for that burlesque of it with which Lord Salisbury amused the public. The Origin of Species does not assume, as a requisite, the chance meeting of similarly varied individuals; and in Chapters III. and VI. of Mr. Wallace's Darwinism, where are assigned evidences which have accumulated since Mr. Darwin wrote, there are described processes quite other than that which Lord Salisbury describes. After referring to artificial selection, and implying that the success of breeders in producing a desired variety depends on their skill "in bringing the right mates together," he goes on to ask:—
"But in natural selection who is to supply the breeder's place? . . . What is to secure that the two individuals of opposite sexes in the primeval forest, who have been both accidentally blessed with the same advantageous variation, shall meet, and transmit by inheritance that variation to their successors?"
Even in the absence of the expositions above referred to, knowledge of familiar facts should have excluded this representation of the requirements. The contents of stud-books and herd-books might have been expected to suffice. It needs but to remember the care with which is specified a descent from some noted sire which lived several generations ago, to recognize the prevailing belief that a variation existing in a particular animal is transmitted in a greater or less degree to posterity, quite apart