Abstract

Biological rhythms, biological Clocks and other photoregulated phenomena constitute the subject matter of photoperiodism in orgmilsm, As a field of scientific inquiry animal photoperiodism has shown a tremendous growth during the past to. decades or so» Today, the amount of work devoted to this field of study has nar,·owed the mechanism of control to hormonal basis. The hormones involved here are the serotonin and melatonin complex synthesized in the pineal gland. But in no animal are the details of the mechanism of the biblogical rhythm fully understood. More generally it seems extremely plausible that the N-aceltty\transterase (enzyme) could either by the periodic depletion of the pineal stores of serotonin or by the periodic output of melatonin from this tie gland synchronised©i@is functioning of ti cells throughout an entire organism.