1. Isolated preparations of the columns of Calliactis and Metridium take up a basic extended length and show repeated contractions at intervals of a few minutes to half an hour. The preparations respond to stimuli with slow movements whose latencies range from about 20 sec. to 2 min.
2. Direct contractions and higher tonus of the preparations are caused by excess K+ and by Mg2+-free sea water; excess -Ca2+ raises tone slightly.
3. Activity is greatly enhanced by Mg2+-free water, and moderately enhanced by excess K+ and excess Ca2+. It is abolished by excess Mg2+ and Ca2+-free sea water, but not by sea water free of both Ca2+ and Mg2+. In K+-free sea water and in Na+-free sea water activity declines slowly and responses to stimuli still occur for at least 1 hr.
4. Except for some enhancement by excess Ca2+ and the depression with excess Mg2+ and Ca2+-free sea water, responses to stimuli are not much affected by ions.
5. Acetylcholine and associated drugs, and also histamine, 5-hydroxytryptamine, and many other substances, have no significant effects on the tone, activity, or responses of column preparations.
6. Adrenaline raises tonus at a concentration of 1 x 10-6; at 1 x 10-5 and above; it causes direct contractions, enhanced activity and high tonus, but it has no effect on responses to stimuli. Noradrenaline, dopamine, tyramine, and other related compounds, as well as various adrenergic blocking agents, are totally inactive.
7. Tryptamine, at concentrations of 1 x 10-4, causes direct contractions, high tonus and enhanced responses to stimulation. 5-Methoxytryptamine has similar effects.
8. To be effective, treatments must be applied directly to the contractile part of the preparation. Applying the active ions and drugs to attached strips of column has no effect.
9. Some comparative and functional aspects of the results are discussed.