Eggs of the Japanese quail, Coturnix coturnix japonica were collected over a five-day period and incubated simultaneously, in accordance with currently accepted commercial practice. After 33 hours of functional incubation, the embryos were fixed and the somites counted to determine the age of the embryo. A great range of variation was encountered, supporting earlier published work. This variability, however, was not random, but inversely related to the length of time the eggs were “held” before incubation. This study suggests that the practice of “holding” eggs be discontinued in all work where uniformity of developmental stages is essential.