. Poultry production. Poultry. THE INCUBATION OF THE EGO 169 is true also. If the temperature is somewhat above 103° F., germination proceeds more rapidly. For instance, twenty- four hours at 104° F. to 107° F. gives a chick which is equal in development to one incubated for three days at 103° F. As soon after laying as the egg is placed at a normal incu- bating temperature, cell division proceeds rapidly, and the cells form themselves into three layers which, from without to within, are referred to as the ectoderm, mesoderm, and endoderm. These three layers are the beginnings of three distinc
. Poultry production. Poultry. THE INCUBATION OF THE EGO 169 is true also. If the temperature is somewhat above 103° F., germination proceeds more rapidly. For instance, twenty- four hours at 104° F. to 107° F. gives a chick which is equal in development to one incubated for three days at 103° F. As soon after laying as the egg is placed at a normal incu- bating temperature, cell division proceeds rapidly, and the cells form themselves into three layers which, from without to within, are referred to as the ectoderm, mesoderm, and endoderm. These three layers are the beginnings of three distinct divisions of the body. Fig. 81 '. Appearance of a chick embryo after twenty-four hours in an incubator. (Courtesy of Kansas Experiment Station.) From the ectoderm, the skin, feathers, beak, claws, ner- vous system, lens, and retina of the eye and linings of the mouth and stomach are formed. The bones, muscles, blood, reproductive and excretory organs develop from the mesoderm, while the endoderm produces the linings of the digestive tract and the respiratory and secretory organs. At about the twenty-fourth hour of incubation a membrane called the amnion develops and gradually surrounds the growing embryo. This amnion is filled with a colorless. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lippincott, William Adams, 1882-1931. Philadelphia, Lea & Febiger
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