Abstract
Selection was carried out for increased ovulation frequency in 2 flocks; under ahemeral (9 generations of selection) or normal (8 generations) light-dark cycles. By the use of an ahemeral regime, the barrier to progress imposed by the limit of 1 ovulation in each light-dark cycle was evaded. Both flocks achieved a considerable increase in oviposition frequency, but so far there has been little evidence of any advantage in this respect due to the ahemeral regime. There was a marked correlated decrease in egg weight in both flocks.