DADDI (1896) observed that animal tissues were colored by Sudan III, a fat soluble dye. Later Riddle (1908), Gage and Gage (1908), Rogers (1910), and, more recently, Warren and Conrad (1939) used the deposition of this dye in egg yolk to study yolk growth. Warren and Conrad injected the dye directly into the blood stream of the chicken instead of feeding it as did the other investigators. Rogers (1910) fed Rhodamine Red, Auramine Yellow, and Saf(f)ranine Red as well as Sudan III. The Rhodamine Red colored the shell and the white of the egg and tinted the yolk slightly. The other two dyes were deposited only in the yolk.Grossfeld and Kanitz (1935) fed Regina Red, a coal-tar dye, to laying chickens and found that some of the dye was deposited in the yolks of the resulting eggs. These workers also outlined a chemical method for the determination of coal-tar .