How does a chick embryo develop?
One of the greatest miracles of nature is the transformation of the egg into the chick. A chick emerges after a brief three weeks of incubation. The complexity of the development cannot be understood without training in embryology. When the egg is laid, some embryonic development has occurred and usually stops until proper cell environmental conditions are reestablished for incubation to resume. At first, all the cells are alike, but as the embryo develops, cell differences are observed. Some cells may become vital organs; others become a wing or leg. Soon after incubation begins, a pointed thickened layer of cells becomes visible in the caudal or tail end of the embryo. This pointed area is the primitive streak, and is the longitudinal axis of the embryo. From the primitive streak, the head and backbone of the embryo develop. A precursor of the digestive tract forms; blood islands appear and later develop into the vascular or blood system; and the eye begins. On the second day of incu
