Dr. Jennings’s researches show that no such implication can be accepted unless we are prepared to cast aside the trammels of reasonable caution. In the first place, the whole matter of feeding appears to be referable to simple organic behaviour not necessarily involving consciousness. The cilia in the mouth-groove and funnel constantly wave in such a manner as to drive a current of water, together with any particles which float therein, towards the interior; and the particles are then engulphed, no matter what their composition may be. Digestible or indigestible, in they go. There is no selection of the one or rejection of the other. But, as we have seen, the Paramecia collect around a bacterial clot and feed upon it. Surely here there is selection of the nutritious! Apparently not. They collect in just the same way towards a piece of blotting-paper, cotton-wool, cloth, sponge, or other fibrous body, and remain assembled round such an innutritious centre just as long as round a bacterial clot. There seems to be no choice in the matter; contact with any substance gives rise, as an organic response, to the lessening or cessation of the regular movements in all the cilia except those of the mouth-groove and funnel. As the Paramecia swim hither and thither, first one, then another, then more, chance to come in contact with the bacterial clot, the blotting-paper, or other substance, and since the lashing of the cilia is then automatically lessened, there they stay; others find their way to the same spot in the course of their random movements, and they, too, stay; thus many soon collect. But this does not account for the seemingly social assemblages of Paramecia where there is no such substance to arrest their progress. Dr. Jennings attributes this to the fact that a dilute solution of carbon-dioxide has, what we may call for the present, an attractive influence. If a bubble of air and a bubble of carbon dioxide be introduced into the water in which Paramecia are swimming beneath a cover-glass, the animalcules collect around the carbonic dioxide, but not around the air bubble. At first they press up close to the bubble of carbon dioxide, but gradually form a ring farther and farther from its limiting boundary. This is held to be due to the fact that it is only the dilute solution of carbonic acid that has the peculiar “attraction”--a stronger solution has a different effect. And, as the gas dissolves, the Paramecia collect in a ring just where the solution is sufficiently dilute.