adapted to nobler employment. Condillac observed that, of all created beings, that one which has least intelligence is least adapted to deceive itself ; an idea borrowed from Hobbes, who defines imagination as decaying sense. Part of the course of this world is a transition from instinct to reason, and it is the mutual conflict of these two principles that causes some errors from which perfect reason is as free as perfect instinct is. So extensive is the variety among created beings, that we cannot well understand the unity by which it is governed, nor the successive advances which it constitutes, and by which it is comprehended. This progress is, in part, a continual passage from the passive to the active state. The Aphides being comparatively rather passive than active, do not manifest those passions which in other animals would seem to have typified the succeed- ing existence and degradation of human nature. When a creature is entering into a higher state of existence, it loses those propensities and the functions of corresponding organs by which its former condition was characterized, — typical of man's ceasing from his earthly motives and employments when he departs to a more exalted life. Or, as it is expressed by Rathke, "When, through the retrograde metamorphosis, a part has shrunk up or even completely disappeared, another has normally formed itself, which compensates for it, or undertakes its function." The existence of Aphides for many successive generations represents the life of a single individual belonging to another tribe of insects. In the latter case every successor equals its original, but in the former instance it happens only occasionally that the oflfspring attains perfection, or ascends to a state equal to that whence it first emanated.
"Tel aux derniers canaux arrive dans sa course,
Le sang revient au coeur et remonte a sa source."
In most insects every individual advances in organization to the limits of its sex and of its species, but in the Aphides a number of individuals are associated together succes- sively or by descent as the means of progress. In creatures of still lower organization, such as sponges, a number of individuals are associated together contemporaneously, and form one compound structure ; while in vegetables association prevails over indi- viduality, which almost disappears. Man, in whom all the variations of animals are represented, condensed, or summed up, has the endowment of individuality or of inde- pendence in the gift of genius, which, if wisely used, tends to discover and to promote truth.
Urtica Linn. Nettle.
Species infested. U. dioica, Linn. Common nettle.
Found beneath the leaves of the nettle at the end of February, 1846. It is then of a very pale green colour, almost white. The young ones are pale green ; the antennæ and tarsi somewhat darker, semitransparent, so that the vessels within, of a bright green colour, are visible. The head is nearly white ; the antennae are setaceous, white, or very pale green, much longer than the body ; the tips of the basal and the whole of the apical joints are pale fuscous : the mouth is pale green and extends to the base of the middle legs : the eyes are bright red, prominent : the segments on the back of the ab- domen are distinct, transverse, nearly equal in size, but they are less distinct, and more
