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optic nerve. The shadow of a hand passing over the abalone in an aquarium causes the animal to contract the head end of the body. Hence the abalone differentiates various intensities of light and thus possesses a primitive sense of sight. The contractile tentacles running out in every direction from the ruff are end-organs of touch. Each has a nerve connected with either the right or left pedal cord. These two centers of innervation run through the middle of the foot for the greater part of its length and are connected by cross fibers. They not only recivereceive [sic] stimuli from the sense organs of the ruff, but govern the multitude of muscle fibers which form the foot.

Scattered all over the exposed parts of the body are long spindle shaped cells which may respond to such mechanical and chemical stimuli as to make of them indefinite end-organs of touch and smell. In the floor of the mantle cavity a water-testing sense organ, the osphradium, extends along the base of each gill. The cells of this simple end-organ are chemically stimulated in such manner that the abalone has sensations of smell, warning it to shut off the incurrent water, when foul or containing some poisonous matter.

If a piece of kelp is held motionless in front of the body, the animal soon responds by reaching out the cleft anterior portion of the foot. These finger-like processes grasp the sea-weed and pull it back beneath the mouth and foot, where it is firmly held. Cells in the mucous lining of the mouth cavity are stimulated so that the animal gets the sensation of taste. Covering the tongue is a long horny, file-like structure, the radula, with many thousands of chitinous teeth symmetrically