the second power (compound plants--plants of the third order). The simple plant proceeding from the combination of the elementary individuals is then termed a bud (_gemma_), in the composition of plants of the third order." The animal kingdom presents still greater difficulties. When, from sundry points on the body of a common polype, there bud out young polypes which, after acquiring mouths and tentacles and closing up the communications between their stomachs and the stomach of the parent, finally separate from the parent; we may with propriety regard them as distinct individuals. But when in the allied compound _Hydrozoa_, we find that these young polypes continue permanently connected with the parent; and when by this continuous budding-out there is presently produced a tree-like aggregation, having a common alimentary canal into which the digestive cavity of each polype opens; it is no longer so clear that these little sacs, furnished with mouths and tentacles, are severally to be regarded as distinct individuals. We cannot deny a certain individuality to the polypedom. And on discovering that some of the buds, instead of unfolding in the same manner as the rest, are transformed into capsules in which eggs are developed--on discovering that certain of the incipient polypes thus become wholly dependent on the aggregate for their nutrition, and discharge functions which have nothing to do with their own maintenance, we have still clearer proof that the individualities of the members are partially merged in the individuality of the group. Other organisms belonging to the same order, display still more decidedly this transition from simple individualities to a complex individuality. In the _Diphyes_ there is a special modification of one or more members of the polypedom into a swimming apparatus which, by its rhythmical contractions, propels itself through the water, drawing the polypedom after it. And in the more differentiated _Physalia_ various organs result from the metamorphosis of parts which are the homologues of individual polypes. In this last instance, the individuality of the aggregate is so predominant that the individualities of its members are practically lost. This combination of individualities in such way as to produce a composite individual, meets us in other forms among the ascidians. While in some of these, as in the _Clavelina_ and in the _Botryllidæ_, the animals associated are but little subordinated to the community they form, in others they are so combined as to form a compound individual. The pelagic ascidian _Doliolum_ is an example. "Here we find a large individual which swims by contractions of circular muscular bands, carries a train of smaller individuals attached to a long dorsal process of the test. These are arranged in three rows: those constituting the lateral row have wide mouths and no sexual organs or organs of locomotion--they subserve the nutrition of the colony, a truth which is illustrated by the