The cell proliferation process in chick embryos was monitored using fluorometry. The 410 nm-excited emission spectra of albumin from controlled and incubated eggs were measured. A strong emission near 622 nm was observed, which is the characteristic emission of protoporphyrin IX (PPIX). It was found that the metabolic level of PPIX for the initial phase increases linearly with the embryonic development time (t) as MPPIXl(t)=MPPIX0+at, where a is a factor proportional to the rate of PPIX accumulation and MPPIX0 is the initial value of MPPIXl(t), suggesting a possible method for estimating the stages of the organ development.