Daily Rhythmic Activity of the Sea-pen Cavernularia obesa Valenciennes. XIX. Further Considerations on the Mechanism of the Circadian Rhythmic Activity

Abstract

A general description of circadian rhythm of the sea-pen is given. The mechanism which supposedly maintains this circadian rhythm is explained. The periodic change of hydrogen ion concentration of body fluid which occurs with expansion and contraction of the animal is proposed as the mechanism which maintains the circadian rhythm of the sea-pen. This idea may be a kind of metabolic theory. Some difficulties for this theory are examined, and, despite these difficulties, the reality of the metabolic theory is again emphasized and the reasons for supporting this theory are explained. Some other considerations on the circadian rhythm of the sea-pen are also presented and the recent literature which seems to support the metabolic theory is reviewed.