In the snail and muscle, the residuum of the coral reappears, but refined and ennobled into a part of the animal. The whole class is characterised by the separation of the fluid from the solid. On the one side, a gelatinous semi-fluid; on the other side, an entirely inorganic, though often a most exquisitely mechanised, calcareous excretion.
Animalization in general is, we know, contra-distinguished from vegetables in general by the predominance of azote in the chemical composition, and of irritability in the organic process. But in this and the foregoing classes, as being still near the common equator, or the punctum indifferentiæ, the carbonic principle still asserts its claims, and the force of reproduction struggles with that of irritability. In the unreconciled strife of these two forces consists the character of the _Vermes_, which appear to be the preparatory step for the next class. Hence the difficulties which have embarrassed the naturalists, who adopt the Linnæan classification, in their endeavours to discover determinate characters of distinction between the vermes and the insecta.
But no sooner have we passed the borders, than endless variety of form and the bold display of instincts announce, that Nature has succeeded. She has created the intermediate link between the vegetable world, as the product of the reproductive or magnetic power, and the animal as the exponent of sensibility. Those that live and are nourished, on the bodies of other animals, are comparatively few, with little diversity of shape, and almost all of the same natural family. These we may pass by as exceptions. But the insect world, taken at large, appears as an intenser life, that has struggled itself loose and become emancipated from vegetation, _Floræ liberti, et libertini!_ If for the sake of a moment's relaxation we might indulge a Darwinian flight, though at the risk of provoking a smile, (not, I hope, a frown) from sober judgment, we might imagine the life of insects an apotheosis of the petals, stamina, and nectaries, round which they flutter, or of the stems and pedicles, to which they adhere. Beyond and above this step, Nature seems to act with a sort of free agency, and to have formed the classes from choice and bounty. Had she proceeded no further, yet the whole vegetable, together with the whole insect creation, would have formed within themselves an entire and independent system of Life. All plants have insects, most commonly each genus of vegetables its appropriate genera of insects; and so reciprocally interdependent and necessary to each other are they, that we can almost as little think of vegetation without insects, as of insects without vegetation. Though probably the mere likeness of _shape_, in the _papilio_, and the papilionaceous plants, suggested the idea of the former, as the latter in a state of detachment, to our late poetical and theoretical brother; yet a something, that approaches to a graver plausibility, is given to this fancy of a flying blossom; when we reflect how many plants depend upon insects for their fructification. Be it remembered, too, that with few and very obscure exceptions, the irritable power and an analogon of voluntary motion first dawn on us in the vegetable world, in the stamina, and anthers, at the period of impregnation. Then, as if Nature had been encouraged by the success of the first experiment, both the one and the other appear as predominance and general character. THE INSECT WORLD IS THE EXPONENT OF IRRITABILITY, AS THE VEGETABLE IS OF REPRODUCTION.