Passing now to creatures of lower organization, it is exceedingly difficult so to divest ourselves of our own special mental garments as to imagine what their simple and rudimentary constructs are like. Perhaps we may fairly surmise that, as visual, olfactory and auditory organs develop, and differentiate from a common basis of more simple sensation, the process of outward projection has its rudimentary inception. The earthworm, which finds its way to favourite food-stuffs buried in the earth in which it lives, would seem to possess the power of outward projection in a dim and possibly not very definite form. Through their marginal bodies--simple auditory or visual organs--the medusæ may have a rudimentary form of this capacity. In any case, they seem to have the power of localization. Mr. Romanes says,[GS] "A medusa being an umbrella-shaped animal, in which the whole of the surface of the handle and the whole of the concave surface of the umbrella is sensitive to all kinds of stimulation, if any point in the last-named surface is gently touched with a camel-hair brush or other soft (or hard) object, the handle or manubrium is (in the case of many species) immediately moved over to that point, in order to examine or brush away the foreign body." And the same author thus describes[GT] the process of discrimination in the sea-anemone: "I have observed that if a sea-anemone is placed in an aquarium tank, and allowed to fasten upon one side of the tank near the surface of the water, and if a jet of sea-water is made to play continuously and forcibly upon the anemone from above, the result, of course, is that the animal becomes surrounded by a turmoil of water and air-bubbles. Yet, after a short time, it becomes so accustomed to this turmoil that it will expand its tentacles in search of food, just as it does when placed in calm water. If now one of the expanded tentacles is gently touched with a solid body, all the others close around that body in just the same way as they would were they expanded in calm water. That is to say, the tentacles are able to discriminate between the stimulus which is supplied by the turmoil of the water, and that which is supplied by their contact with the solid body, and they respond to the latter stimulus notwithstanding that it is of incomparably less intensity than the former." Here, in discrimination, we reach the lowest stage of mental activity. It is exceedingly difficult, however, to determine how far such simple responses to stimuli are merely organic, and how far there enters a psychological element.