malcula infusoria became, by a vital oxydation, granular in the polypi. This granulation formed itself into distinct organs in the molluscæ; while for the snails, which are the next step, the animalized lime, that seemed the sole final cause of the life of the polypi, assumes all the characters of an ulterior purpose. Refined into a horn-like substance, it becomes to the snails the substitute of an organ, and their outward skeleton. Yet how much more manifold and definite, the organization of an insect, than that of the preceding class, the patient researches of Swammerdam and Lyonnet have evinced, to the delight and admiration of every reflecting mind.
In the insect, for the first time, we find the distinct commencement of a separation between the exponents of sensibility and those of irritability; i.e. between the nervous and the muscular system. The latter, however, asserts its pre-eminence throughout. The prodigal provision of organs for the purposes of respiration, and the marvellous powers which numerous tribes of insects possess, of accommodating the most corrupted airs, for a longer or shorter period, to the support of their excitability, would of itself lead us to presume, that here the vis irritabilis is the reigning dynasty. There is here no confluence of nerves into one reservoir, as evidence of the independent existence of sensibility as sensibility;—and therefore no counterpoise of a vascular system, as a distinct exponent of the irritable pole. The whole muscularity of these animals, is the organ of irritability; and the nerves themselves are probably feeders of the motory power. The petty rills of sensibility flow into the full expanse of irritability, and there lose themselves. The nerves apper-
