(1)In order to study the effects of light on the ovulation as well as the behavior of egg-laying in ring doves, they have been kept in a dark room of an area of 3780 square feet, where three 100 W electric lamps are able to be turned on throughout the night, and inversely, they are to be turned out throughout the day. This lightening is carried out automatically with a time switch made in Switzerland. Thus, night and day are reversed completely in the dark room. (2) Ring doves breed successfully in the dark room adapting themselves to the environment artificially arranged, and they lay the first eggs of clutch toward the end of daytime of the room, and second ones in the beginning of daytime two days later. The time interval which is necessary for the adaptation has been found to be more than three days, but less than 7 days, counting from the day of laying of the first egg of clutch. (3) It was foud that there exists a relation between the light and the ovulation in ring doves. When ring doves are transferred from normal cages to those in the dark room at the time of 27-34 hours before the laying of first eggs of clutch the dark room being dark, the second ovulation of the clutch delay presumably more than ten hours, the second egg-laying of clutch occurring from fifty to seventy hours after the first egg-laying. (4) Consideration on the delay of the ovulation of the second ovum of clutch in such situations was made by the writers in reference to hormones of anterior and posterior lobes of pituitary as well as progesterone.
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