It is the necessary result of the imperfection of our intellect, and one of the dominant conditions of overruling time, that one thing must follow the other. It is, therefore, neither an expressed nor even an implied inferiority that puts one species before the other in a generic group; or one genus before the other in their successive order. Affinities may lead both species and genera in varying directions, although treated descriptively as of linear succession, in which order they are usually arranged, but this is unavoidable and therefore not derogatory. It is for the mind to conceive their radiation from a type, or their parallelism with other forms, even in the connection of affinity, and not merely of analogy, for the latter can be expressed even in arrangement.
Thus encouragement attends the beginner at the very outset of his study, and the prospect of a wide field for discoveries, in all directions, lies open to him.
The FAMILY, after the GENUS, is the next natural group at which we arrive, proceeding synthetically. Its characters, succeeding to those of the ORDER, group together collectively the largest numbers of forms that in their several combinations are the most nearly equivalents, and may be almost paralleled in that quality to the alliance of species. Ascending from species, the naturalist scarcely hopes to find in the groups formed above them strict parallelism, although, to be logical, it should be so, and, where the combinations are most natural, it is most nearly so. Thus we do not again distinctly reach equivalents until we arrive at these families, which from linking together associations usually combined by an identity of instinct and functions, attach to themselves greater interest, and form alliances pointed out by the finger of nature itself, which are therefore exempted from the arbitrary caprice of the constructive systematist.
It does not follow that families should be even nearly numerically equivalent, for a family may contain a few or a multitude of genera and species, or a multitude of genera and few species, or also a multitude of species and few genera. Families comprise groups of forms to which nature delegates the execution of certain duties and offices, and whether specifically numerous or few, we may assume they are sufficient for the object intended. If we can reach the motive that controls the peculiarities of the group, it is a golden key to the explanation of the structure of its constituents, and, perhaps might furnish us, if not with a positive clue, yet with a surmise as to the functions of the collateral groups of which it forms a member, and which diligent observation may accurately determine.