| Abstract: | White Leghorn eggs were incubated to desired prevasular stages. Each embryo, upon its intact yolk and surrounded by albumen, was rolled from the shell into a sterile 50 ml beaker. In an uppermost position, the blastoderm was lightly stained with neutral red. Three types of localized cuts were made as indicated below, and the beaker-embryo unit placed in a sterile humidified chamber for further incubation. Results: (1) Unilateral cuts adjacent to the body and parallel with its axis blocked or suppressed formation of the vitelline artery on the cut side, even though healing occurred; (2) A specific site was found in the area pellucida opposite the sinus rhomboidalis which, when lightly cut perpendicular to the body axis, resulted in blockage or shifting of the final junction between aorta and vitelline artery as far cephalad as the thirteenth somite level. Formation of a dual final junction with the aorta also occurred. (3)Transverse cuts through the body axis and into the area pellucida bilaterally, frequently resulted in bilateral blockage or bilateral shifting. In still other cases, growth of a functional loop around the cut to connect the aortae in anterior and posterior segments with the vitelline artery were observed. Other unique circulatory patterns are described. Apparently, slight interference with the capillary plexus which precedes the vitelline artery causes anomalous development. Circulation is considered a major factor in arterial differentiation. Cutting probably alters the plexus and relation of its components to the onset of blood flow. |
