Effects of temperature-fasting on the structural organisation of chick embryos.

1. The progressive effects of temperature fasting on the blastoderms of chick have been studied. 2. The blastoderms do not show any morphogenetic change up to the 7th day of delay prior to incubation. Embryological changes in form of suppression arise in the organisation of blastoderms delayed over 12 days or more. The axes of the embryos tend to be more shortened in the further delayed embryos. 3. The axial structures of the blastoderms suffer reduction in shape and size until they disappear in the blastoderms kept waiting for 15 to 20 days. The blastoderms enlarge into a sheet-like structure without any mark of organisation. 4. The blastoderms become gradually incapacitated beyond the temperature-fasting for over 20 days. 5. The probable mechanism of these morphogenetic features have been sought in the denaturation of "Cell substances" by dehydration, suppression of mitotic activities and morphogenetic movements of cells of the blastoderms.