68 H. JEANETTE ALLEN. 



EXPLANATION OF PLATE I. 



FIG. i. Yolk-sac of a six-somite chick before development of the vascular 

 area. Glycogenated cells in black. 



FIG. 2. Splanchnopleure of the vascular area of a six-day chick with glycogen 

 in the walls of the blood-vessels (stippled), bl. v., blood-vessels; coel., coelome; 

 y.s., yolk-sac. 



FIG. 20. Vascular area of a seventy-two-hour chick under high power. (Gly- 

 cogen stippled.) 



IG. 2b. Vascular area of a four-day chick, high power. Actual masses of 

 ogen represented in black. 



FIG. 3. Glycogen (stippled) in the ectoderm of a chick with six somites, eel., 

 ectoderm. 



FIG. 4. Glycogen (stippled) in the heart tubes of a chick with nine somites. 

 lit., heart; ph., pharynx. 



FIG. 5. Heart of a six-day chick with glycogen abundant in the muscular walls. 

 (Stippled.) La., left auricle; l.v., left ventricle; r.a., right auricle; r.v., right ven- 

 tricle. 



FIG. 50. Wall of a four-day chick's heart under high power. The black por- 

 tions represent glycogen. 



FIG. 56. Ten-day chick's heart. High power. Globules of glycogen in black. 



FIG. 6. Fore-gut of a four-and-a-half-day chick just anterior to the anterior 

 portal. (Glycogen stippled.) ent., entoderm; /. g., fore-gut. 



FIG. 7. Posterior intestinal portal of a seven-day chick. (Glycogen stippled.) 

 p.i.p., posterior intestinal portal. 



FIG. 70. Hind-gut and splanchnic entoderm of the same, a few sections pos- 

 terior to 7. (Glycogen stippled.) ent., entoderm; h.g., hind-gut. 



FIG. 8. Cross section through intestine of a ten-day chick. (Glycogen stippled.) 



