The large divisions of nature appear simple and distinct enough in their great frame, but when we approach their confines, close investigation discovers analogies and affinities, which, where the separation seems most apparent, create insuperable difficulties, and render linear succession, or distinct division, nearly an impossibility. _Here_ we find parallelism, and _there_ radiation, and elsewhere a complicated reticulation without subordination; and this is one of the great problems, which it is the office of the mature naturalist to endeavour to solve. The present work has to do, however, with but one small portion of the whole. Thus we see that, in order to arrive at a knowledge of natural objects, a method must be pursued to avoid being overwhelmed by their multiplicity, whereby confusion would be produced in the mind which their methodical investigation tends to dissipate. Their abundance precludes the possibility of their being all equally well known, although it is very desirable to have a general, if even superficial acquaintance with them, that is to say, in the broad and distinguishing features of their large groups, for as to an accurate knowledge of all their species, it would be futile to attempt it. Possessing this general knowledge, the attention may be turned with greater advantage in any special direction, and that pursued to its entire acquisition. Natural objects have been arranged in KINGDOMS, ORDERS, CLASSES, FAMILIES, and GENERA, all deduced in their successive and collateral groups from characters exclusively derived from SPECIES; therefore to the accurate knowledge of _species_ all endeavours must be directed, they comprising within themselves all the rest, although the characters upon which they themselves depend for separation from their congeners are the most trivial of any. Each combination, in its analytical descent, contains characters of wider compass than those which succeed it, and consequently embraces in that descent more species than the successive divisions; just as in the ascent, or synthetical method, the characters of every successive group gradually expand. Species being thus the only real objects in nature from which all knowledge springs, and in which exclusively all uses lie, other combinations being perhaps as merely imaginary as are the many lines which are drawn over the surface of the globes, it would imply that subdivisions merely lend aid to acquire more rapidly the details upon which they depend. We will, therefore, first turn our attention to species.