(a) Morphology of cultured erythroid cells on day 0, 1 and 3 of differentiation. Erythroblasts were purified from embryonic liver (E14.5) and incubated for the indicated times in erythrocyte differentiation medium. The cells were stained with a Diff-quick kit. (b) Percentage of cells without nuclei (Syto16low cells) on the indicated days of differentiation (mean±s.d., n=6). Loss of nuclei occurred normally in all mice. 