DIURNAL CHANGES IN ACTIVITIES AND GEOTROPISM IN THYONE BRIAREUS

Abstract

Thyone briareus observed during the winter months exhibited certain definite diurnal periods of activity. (1) Between about 4:00 P. M. and 1:00 to 2:00 A.M. the frequency of "locomotor" waves increased in number and the feeding movements of the tentacles were more numerous than at other periods of the day, even when observed in the dark under red illumination. (2) When during the late evening hours Thyone was rotated in a vertical plane, locomotor waves coursed negative to gravity regardless of which end of the animal was oriented downward. Since it was found that waves of contraction could be elicited experimentally at almost any region by producing tensions in the body wall when Thyone was in a horizontal position, it is supposed that the sensitivity of the body wall is so altered during the late evening hours that tensions produced in the body wall when the animal was placed in a vertical position are sufficient to bring about the formation of locomotor waves at the lower end. Absence of statocyst function is suggested by these experiments, and by additional experiments with eviscerated animals which still can be made to exhibit negative geotropism. During spring and summer months the activity of Thyone was not so definitely marked off into diurnal periods, neither was the negative geotropic response regularly obtained.