If, instead of a faintly acid drop, a little alkaline liquid be introduced beneath the cover-glass, the Paramecium similarly jerks backward and turns aside on reaching its outer boundary. The turning may carry it away from the alkali, as shown in Fig. 2, V.; but it just as often brings it again towards the drop, especially a large one. It seems to be a matter of chance which result follows. But eventually the little creature sails off, since each time it comes within the influence of the alkaline fluid it jerks back and turns. It appears, then, that when it is swimming in a normal solution a faintly acid liquid does not much modify its behaviour, but an alkaline fluid evokes a reversal of the cilia; and that when it is a slightly acid solution, not only does stronger acid cause reversal, but normal fluid produces a similar result. A reaction of essentially the same kind is in fact called forth by such different stimuli as chemical substances, water heated above the normal temperature, or cooled considerably below it, and fluids which cause changes of internal pressure within the substance of the cell. Nor does it matter where the stimulus is applied. If it be applied at the hinder end the infusorian still jerks backward, though this may drive it into a destructive solution and thus cause death. There is, however, some evidence of different behaviour in some infusorians according as the stimulus is here or there. In other words, the behaviour is to some extent related to the position of the part stimulated. Furthermore, it may be gathered from Dr. Jennings’s account that there is nothing to lead us to suppose that such free living cells show any indication of what may be regarded as the keynote of intelligent behaviour. They do not profit by experience. They exhibit organic reactions which may be accompanied by some dim form of consciousness, but which do not seem to be under the guidance of such consciousness, if it exist. One of the first lessons which the study of animal behaviour, in its organic aspect, should impress upon our minds is, that living cells may react to stimuli in a manner which we perceive to be subservient to a biological end, and yet react without conscious purpose--that is to say, automatically. The living cell assimilates food and absorbs oxygen, it grows and subdivides, it elaborates secretions, produces a skeletal framework or covering, rids itself of waste products, responds to stimuli in a definite fashion, moves hither and thither at random, its functional activities being stimulated or checked by many influences; and yet this varied life may give no evidence of a guiding consciousness: if purpose there be, it lies deeper than its protoplasm, deeper than the dim sentience which may be present or may be absent--we cannot tell which.