this exposition that being determined by mere motivation presupposes a certain width of the sphere of knowledge, and consequently a more fully developed intellect: therefore it is peculiar to the higher animals, quite pre‐eminently, however, to man; while being determined by instinct only demands as much intellect as is necessary to apprehend the one quite specially determined motive, which alone and exclusively becomes the occasion for the manifestation of the instinct. Therefore it is found in the case of an exceedingly limited sphere of knowledge, and consequently, as a rule, and in the highest degree, only in animals of the lower classes, especially insects. Since, accordingly, the actions of these animals only require an exceedingly simple and small motivation from without, the medium of this, thus the intellect or the brain, is very slightly developed in them, and their outward actions are for the most part under the same guidance as the inner, follow upon mere stimuli, physiological functions, thus the ganglion system. This is, then, in their case excessively developed; their principal nerve‐stem runs under the belly in the form of two cords, which at every limb of the body form a ganglion little inferior to the brain in size, and, according to Cuvier, this nerve‐stem is an analogue not so much of the spinal cord as of the great sympathetic nerve. According to all this, instinct and action through mere motivation, stand in a certain antagonism, in consequence of which the former has its maximum in insects, and the latter in man, and the actuation of other animals lies between the two in manifold gradations according as in each the cerebral or the ganglion system is preponderatingly developed. Just because the instinctive action and the ingenious contrivances of insects are principally directed from the ganglion system, if we regard them as proceeding from the brain alone, and wish to explain them accordingly, we fall into absurdities, because we then apply a false key. The same circumstance, however, imparts to their action a remarkable likeness to that of somnambulists, which indeed is also explained as arising from the fact that, instead of the brain, the sympathetic nerve has undertaken the conduct of the outward actions also; insects are accordingly, to a certain extent, natural somnambulists. Things which we cannot get at directly we must make comprehensible to ourselves by means of an analogy. What has just been referred to will accomplish this in a high degree when assisted by the fact that in Kieser’s “_Tellurismus_” (vol. ii. p. 250) a case is mentioned “in which the command of the mesmerist to the somnambulist to perform a definite action in a waking state was carried out by him when he awoke, without remembering the command.” Thus it was as if he must perform that action without rightly knowing why. Certainly this has the greatest resemblance to what goes on in the case of mechanical instincts in insects. The young