1. By classification is meant an arrangement of organic beings in some systematic manner, according to attributes which they have in common, and which may form the principle of a division into different classes or families. Pointing out that in the early history of botanical and zoölogical science the tendency was to make classifications according to a single characteristic, Mr. Spencer reminds us that later naturalists, by attending to a greater number of characteristics, and finally to the greatest number that can be found to be common to various classes of vegetable and animal organisms, have constructed systems of classification which, in place of a linear or a serial order, have exhibited the alliances of different groups, then the sub-groups, and the sub-sub-groups, so that the divergences and redivergences become developed, while the resemblances which obtain are preserved throughout the whole class. But it is at once apparent that, although classification, on whatever principle it is conducted, may be valuable as a means of fixing in the mind the resemblances or differences of structure that obtain in the different orders of organized beings, as, for example, among the vertebrate or the invertebrate animals, the flowering or the flowerless plants, the seeds naked or the seeds inclosed in seed-vessels, yet that any other system of classification, based upon other resemblances or differences which actually present means of grouping or separating the different families of organized beings, is just as valuable an aid in the investigation of facts. How far any classification affords an argument, or the means of constructing an argument, which will yield a support to the doctrine of evolution superior to that which it yields to the doctrine of special creations, is of course a question.