The organs which we have hitherto been considering, refer exclusively to the individual, and are necessary to the support of the system throughout the whole of life; those which now claim our attention, do not refer to the wants of the individual, but are subservient to the continuation of the species. The instincts by which the organs of reproduction are governed, have been already enumerated, when treating of the active powers of the mind. At present, it only remains for us to enquire into the different modes by which animals are propagated, and the various organs which are called into exercise in each.

The simplest mode of generation does not require sexual organs for the accomplishment of its purpose. Part of an individual drops off, and speedily exercises the functions of an independent being. This is termed Generation by Spontaneous Division. In other cases, a bud is produced from the surface, which gradually evolves, drops off from the parent when ripe, and begins to exhibit a separate life. This is termed Gemmiparous Generation.

In those animals which possess peculiar organs for the preparation of the germ or ovum, some are Androgynous, and either have the sexual organs incorporated, and capable of generating without assistance, or the sexual organs are distinct, and the union of two individuals is necessary for mutual impregnation: others have the sexual organs separate, and on different individuals.