PHOTOPERIODISM IN FEMALE DOMESTIC FOWL 775 



Stated that there were no reports of laying at night by hens maintained 

 under daylight plus continuous night lights, indicating that the lay 

 behavior of hens so lighted differed from that of hens under continu- 

 ous, uniform lighting. This was found to be true, hens "under continu- 

 ous artificial light supplemented by daylight" laying only during the 

 normal daylight period. These and related observations led Warren 

 and Scott to suggest that the influence of light on lay behavior was 

 psychological. 



In comparing the effects of continuous lighting (plus daylight) and 

 periodic increments to daylight, Moore and Mehrhof (1946) re- 

 ported oviposition to be confined to the period of natural daylight. 



(d) Intermittent lights. In the experiments of Wilson and Ab- 

 planalp ( 1956) referred to earlier, lay of eggs was recorded at hourly 

 intervals. Taking totals of eggs laid by all groups under intermittent 

 lighting, the distribution was found to be fairly comparable amongst 

 the six 4-hr periods of illumination. There was, however, a tendency 

 toward concentration of lay at or around the hour at which the hens 

 were subjected to the limited photoperiods. Records for individual 

 hens were not published. 



Light and Other Factors. The restriction of oviposition to rela- 

 tively limited hours of the 24 in hens under continuous and uniform 

 light was attributed by McNally (1946) to activity associated with 

 feeding, by Fraps et al. (1947) to activity associated with "mainte- 

 nance" operations. In the hens observed by Fraps et al., the time of 

 maximal activity was plainly associated with replenishment of feed, an 

 operation performed daily between 8:00 and 9:00 a.m. Although 

 ample feed always remained in the troughs, the arrival of the daily 

 bounty was regularly accompanied by great activity and much noisy 

 anticipation. Toward evening overt activity was much reduced, and 

 little was observed after about 6:00 to 8:00 p.m. 



Bastian and Zarrow (1955) have shown that activity in hens on a 

 1 3-hr photoperiod is largely limited to the photoperiod. But as Ham- 

 mond (1954) observes, it is also true that "activity can vary the pat- 

 tern and exposure to light." Activity undoubtedly determined the pat- 

 tern of relative exposure to light in the hens observed by Fraps et al.; 

 the same was probably true in the experiments described by McNally 

 (1946) and, to a Hmited extent, in those of Wilson and Abplanalp 



