"special creation" of the horses does not look well, it must be confessed, in the face of the gradual and obvious modification exhibited by the series of fossil horses, which leads without a break from Eohippus to the modern horse. At most, it may be said, there is but a choice of probabilities offered us. And in the adoption of a scheme of development, and in face of the facts laid before us, it is hard to see any grounds whereon the special-creation theory can be maintained, or the theory of progressive development and evolution denied. For if evolution is the law of the horse's history, it must logically follow that it represents the scheme of nature throughout: since the uniformity of nature, in which we are bound to believe, and to which we are bound to appeal, would utterly negative the idea that evolution should hold good for the horse, and be inapplicable to any other living thing. Because the missing links are not so completely supplied to us in other cases as in the horse, we are not on that account entitled to assume that the theory of development is invalid. We may not see an oak-tree grow inch by inch, but we are as positive as our mental nature will admit, that the oak was once an acorn, and that there has been a progressive growth and increase which might not be apparent to us were we to watch the tree for weeks together. Applying this reasoning to the case before us, it would be as illogical to deny that the order of nature was that of development, as to insist that the oak was created as it stands. The extent of human knowledge, and the duration of human existence, are together inadequate to enable us to discern the progress of this world's order after the fashion whereby, from a lofty elevation, we may trace every winding of a stream. But the probabilities of the case are as overwhelmingly for progressive development, as the direct evidence at hand—exemplified by the horse's pedigree—tells against special and independent creation having been the way of the First Cause in the making of the world and its living things.
The entire scheme of scientific discovery thus depends very largely upon the use made of the hints which nature is continually presenting to the searcher, and on the correct interpretation of the facts he is fortunate enough to elicit in his search. The study of the rudiments of animal and plant structures may well exemplify, from the importance of its results, the value of gathering up the veriest fragments of knowledge. For, as Mr. A. R. Wallace has remarked regarding rudimentary organs, "There must be a cause for them; they must be the necessary results of some great law." And again are this author's words most appropriate when he says: "Many more of these modifications should we behold, and more complete series of them, had we a view of all the forms which have ceased to live. The great gaps that exist between fishes, reptiles, birds, and mammals (that between reptiles and birds is now wellnigh obliterated) would then, no doubt, be softened down by intermediate groups, and the whole organic world would be seen to be an unbroken and harmonious system."—Gentleman’s Magazine.