Abstract
1. The effect of a short, unchanging day-length of 6 hr. on age at sexual maturity and egg production has been observed. 2. The birds matured at the same age as the controls but at a lower body weight. 3. Egg production over 58 weeks was considerably reduced. 4. An increase in day-length between December and August always increased production. 5. A decrease in day-length between February and August always decreased production; this decrease was greater the later in the year that the change occurred. 6. It is concluded that age at sexual maturity is not affected by the absolute length of the day, and that egg production is affected both by the absolute length and by the change in length.