The percent of cells that were positive for embryonic globins in erythrocytes and cultured erythroblasts. Left, ζ+ cells. Right, ɛ+ cells. RBC, red blood cells; Culture, day 14 of culture; F, fetal; C, cord; A, adult. Note the difference in the y-axis scales for the two embryonic globins. There is an ontogenic decline in the percent positive cells, both in vivo and in culture.