THE STUDY OF INCUBATED EGGS 



The problem of the changes in the egg" during incubation were 

 first taken up. By feeding various dyes to animals certain tissues are 

 colored. Aniline dyes have been used by investigators to show va- 

 rious changes taking place in the tissue. Dyes fed to hens will color 

 parts of the egg. This coloring of the eggs was done to study the 

 changes taking place during the incubation of the egg. The two 

 principal dyes used were Sudan III and Rhodamine Red, Sudan III 

 when fed to fowls apparently colors the fat deposits only. Rhodamine 

 Red colors the shell and albumen of the egg. Sudan III colors the 

 yolk of the egg only, while Rhodamine Red colors the albumen 

 strongly and the yolk but little. In the experiments, 25 milligrams 

 of Sudan III, and 100 milligrams of Rhodamine Red were fed to a hen 

 per day. 



The eggs from the hens fed Sudan III had yolks of a bright red 

 color. Daily feeds produced concentric layers of red alternating with 

 yellow yolk. Even with the dye in all the food no uniformly colored 

 yolks were produced. The eggs laid soon after the first feeding of the 

 dye showed these concentric layers near the outer part only. These 

 two facts show that the yolk is built up by successive layers of fat 

 deposited on the surface of the material already present and not any 

 intermingling of the material. 



When the color was fed at stated intervals, the rate of growth 

 within the yolk was obtained. It was possible in this way to cal- 

 culate the number of days required for the development of the yolk 

 and also to study the relative amount of material added during the 

 stages of its formation. We find that the deposition of the yolk ma- 

 terial is very slow at first, but very rapid at the end, the outer bands 

 being much broader as well as greater in circumference. With the 

 particular fowl observed it required fourteen days for the yolk to be 

 fully formed. This observation was taken during the heavy laying 

 season. 



The germ disc, albuminous center, and connecting tubes were left 

 uncolored, showing that either they contain little or no fat or were a 

 part of the ovary before the dye was. fed. 



The Rhodamine Red dye colors the albumen of the egg principally. 

 There is not enough protein in the yolk to make the color show very 

 distinctly in contrast to the yellow. The albumen is colored uni- 

 formly throughout. 



After two days of incubation the fertile eggs colored with Sudan 

 III undergo a change. The outer bands of color break up and inter- 

 mingle with the yellow bands of the yolk. By the fifth day of incu- 

 bation, the yolk is quite well mixed, so that only a faint resemblance 

 of the banded condition remains. By this time, also, the albumen near 

 the developing embryo has turned pink. The bulk of the albumen, 

 however, is still white. Upon boiling the egg, which is necessary to 

 make the study, the white albumen becomes quite like rubber, while 

 the pink albumen remains very soft. On the third and fourth, and 

 often on the fifth day of incubation it was possible to get the pink 

 albumen to coagulate. The amount of the pink albumen upon which 



