. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 188 MIRIAM F. BENNETT stant darkness were shifted by single illumination periods of varying lengths. The direction and the amount of shift were dependent on the time of day at which the animals were exposed to an illumination of 90 ft. c. A more recent paper (Brown. Fingerman and Hines, 1954) presents an hypothesis to account for the graded series of shifts of the diurnal cycle of color change for Uca. These graded shifts in the phases of the cycle were noted when series of crabs were exposed to various higher illuminations
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 188 MIRIAM F. BENNETT stant darkness were shifted by single illumination periods of varying lengths. The direction and the amount of shift were dependent on the time of day at which the animals were exposed to an illumination of 90 ft. c. A more recent paper (Brown. Fingerman and Hines, 1954) presents an hypothesis to account for the graded series of shifts of the diurnal cycle of color change for Uca. These graded shifts in the phases of the cycle were noted when series of crabs were exposed to various higher illuminations by night and various lower ones by day. Two factors appeared to operate in the altering of the phases: 1) the strength of the light-increase 5 10 DAYS AND 15 20 50-MINUTE 25 30 PERIODS 35 FIGURE 8. An illustration to show the effects of shifts of the tidal cycle of an experi- mental group of clams on the long-term rhythm of activity. The broken line curve is that of the experimental and the solid line one is that of the controls. The broken line arrow indi- cates the time of low tide for the experimental group and the solid line one for the control group. The horizontal arrows indicate the directions and amounts of shifts possible. (For discussion, see text.) and 2) the brightness of the higher illumination to which the animals were exposed by night. Exposures of fiddler crabs to several cycles of altered illumination operate to shift the tidal rhythms of color change as well as the diurnal cycles (Brown, Finger- man, Sandeen and Webb, 1953). Here the phases of the tidal and the diurnal rhythms were moved in the same direction and by the same number of hours. In this case, the temporal relationship which existed between the two cycles at the times of exposure of the crabs was maintained. In the present study, the data lead to the assumption that the tidal rhythm for the experimental group of quahogs was shifted so that its phases occurred about 20 hours earlier than
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
