But what, it may be inquired, is this great primary truth which the monomial system tends to violate? I repeat what I have already stated, that it is the _existence of natural assemblages_ which that scheme would, if it were practicable, discountenance. Order and symmetry, however (which involve classification, or arrangement), are the law of Nature, and it is not possible to set them aside. It matters not if harsh lines of demarcation are undiscernible between the several consecutive groups,--the _groups themselves_ must still remain (however equivocal it may be where they exactly commence or terminate), and cannot be wiped out. To suppose _a priori_ that the allied divisions of the animate creation are perfectly disconnected _inter se_, is in fact to break the chain on which the unity of the organic world depends; whilst to assume that groups cease to be groups when they can be discovered to merge into each other, would no less destroy the harmony of that admirable method, or array, which the naturalist, above all others, delights to contemplate. If things are no longer to be regarded as dissimilar because they unite on their outer limits, differences may be given up, as having no special meaning, and as therefore unworthy of investigation. It requires but a slight insight into the physical universe to be convinced, that nearly everything which we see (and, moreover, _without injuring its individual reality_) is blended into that to which it is the most akin. Night is distinct from day; yet, so long as the twilight intervenes, no man can pronounce where the one ends, and the other begins. Heat is opposed to cold; yet, if by degrees they be respectively diminished, they will at last amalgamate, in a central temperature. And thus it is with things material. The sea and the land are essentially unlike; yet the precise boundary between the two is never clearly defined,--the ebb and flow are constantly going on, and the line of separation is variable. The mountain-range is moulded on a different type to the level country beneath it; yet the turning-point of them both is, in all instances, on neutral ground. We need not however adduce further evidence in support of this fact,--that, throughout the whole of Nature, the _general principle_ of fusion (either absolute or apparent) is most obvious. From first to last, traces of it are everywhere to be detected; not only between _clusters_, or material combinations, of objects (in which case it is absolute), but even between the objects themselves,--under which circumstances, however, it is merely apparent; for, since they are specifically dissimilar, it can only arise from their _near resemblance_ to each other, and not from their positive coalescence. But, admitting that this universal blending, throughout the animate world, does not interfere with the gradual conformation of its several groups, which _therefore_ should be recognized; we may perhaps be told