. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. »A,C,B - Dotes by which beak became black A - None (2) B - Feb. 1,28, Mar. 8,15 C- Feb. 28, War. 8(2) D- Jan. 8(2) E -Jan. 12, 18 SEPT OCT NOV DEC JAN FEB MAR FIGURE 1. Experiments to determine the time of termination of photorefractoriness in bobolinks exposed to the natural day-lengths of Lat. 36° N. At various times between October 2 and November 28, day-length was abruptly increased either to 14 hours daily or to a simulation of the daily change in day-length (sunrise-sunset) occurring at that time in the southern hemisp
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. »A,C,B - Dotes by which beak became black A - None (2) B - Feb. 1,28, Mar. 8,15 C- Feb. 28, War. 8(2) D- Jan. 8(2) E -Jan. 12, 18 SEPT OCT NOV DEC JAN FEB MAR FIGURE 1. Experiments to determine the time of termination of photorefractoriness in bobolinks exposed to the natural day-lengths of Lat. 36° N. At various times between October 2 and November 28, day-length was abruptly increased either to 14 hours daily or to a simulation of the daily change in day-length (sunrise-sunset) occurring at that time in the southern hemisphere. For this treatment groups A and E were moved, at the times indicated, to light-tight compartments indoors ; the other groups remained outdoors, where the artificial lighting was superimposed on the natural day-length. The development of black pigment in the beak is evidence of testicular recrudescence. fluorescent lights (which insured a minimum intensity of 30 to 35 foot-candles ) provided 14-hour daily photoperiods (5:15 AM-7:15 PM) ; these birds remained in the outdoor aviary, hence during the dark period were exposed to approximately normal light of the night sky. Beak pigmentation indicative of testicular recrudes- cence developed first in one bird during the week ending February 1, in the other three before March 15. Group C consisted of three "spring captures"; they were subjected to exactly the same light schedules and other conditions as Group B except that the 14-hour photoperiods were begun almost two weeks earlier, on November 15. Beak pig- mentation developed during the last week of February and first week of March. Group D consisted of two "spring captures"; they were caged in an outdoor aviary where, beginning November 8, incandescent lamps (intensity about 45 foot- candles ) provided photoperiods which approximated the changing sunrise-sunset day-lengths normally occurring during the months of November to March at Lat. 45° S. The abr
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
