In the lamelliforanchiata, instead of a chain of ganglia, as in the medusae, we have three pairs of ganglia : cerebral at the mouth, pedal in the foot, and parietal-splanchnic supplying the bronchial apparatus and viscera. The heart has distinct chambers, but apparently consists of protoplasmic substance without distinct nerves or ganglia. The application to it of an interrupted current will arrest the rhythmical pulsation and cause stoppage in diastole.1 This effect is prevented by atropine. Warmth up to 104° quickens the heart; when raised higher it destroys reflex movement in the animal, and afterwards arrests the heart also. Pure water without salts-quickly paralyses the muscles and causes death in salt-water molluscs. Curare in small doses has no effect, large doses quicken, but do not abolish movement, and do not affect the heart. Strychnine somewhat stimulates-movement, and may cause some local contractions, but never any general tetanus. Nicotine acts in a similar way, but in large doses appears to paralyse the muscles and cause death; it also appears to cause contraction of the vessels, so that the heart becomes more bulky and beats more quickly. Veratrine has a similar action. Digitalis has no action, excepting when applied to the heart directly, and then it renders the beats slower and sometimes stops them. Antiarine, like digitalis, has no general action, but stops the heart if applied to it directly. Muscarine generally causes muscular contractions in the body: first acceleration, quickly followed by retardation of the cardiac beats. Sulphocyanide of potassium diminishes reflex action, but has little effect on the excitability of the nerves. A small dose somewhat quickens the cardiac action; a large dose stops the heart in diastole, and if it is directly applied to the heart the stoppage is permanent.