Effects of accelerating stimulation on different indices of development in Japanese quail embryos.

Effects of continuous accelerating stimulation on the timing, duration and rate of occurrence of different indices of development in Japanese quail embryos were examined. Indices used were: the onset of breathing and hatching, also pipping, clicking, vocalisation, membrane penetration, yolk sac withdrawal and lung aeration. Results showed that embryos stimulated by clicks began breathing about nine hours in advance of unstimulated controls and hatched about 23 hours in advance. All other indices occurred early in comparison with controls but not all occurred at the same accelerated rate and some having begun early, proceeded at the same rate as controls then were completed rapidly just before hatching. Developmental problems are discussed in the light of these results and it is suggested that continuous accelerating stimulation affects development in two main stages.