. The development of the chick; an introduction to embryology. Birds -- Embryology. 74 THE DEVELOPMENT OF THE CHICK The later history of the primitive streak is Figs. 44, 51, 61, 65, etc.: the embryo arises in front of it around the head-process as a center; the anterior end of the primitive strealH marks the hind end of the differentiated portion of the embryo^ As the embryo grows in length the primitive streak decreases (cf. measurements in table), until finally, when the completion of the embryo is indicated by the formation of the tail-fold, the primi- tive streak disappears
. The development of the chick; an introduction to embryology. Birds -- Embryology. 74 THE DEVELOPMENT OF THE CHICK The later history of the primitive streak is Figs. 44, 51, 61, 65, etc.: the embryo arises in front of it around the head-process as a center; the anterior end of the primitive strealH marks the hind end of the differentiated portion of the embryo^ As the embryo grows in length the primitive streak decreases (cf. measurements in table), until finally, when the completion of the embryo is indicated by the formation of the tail-fold, the primi- tive streak disappears. The primitive knot and primitive pit occupy its anterior end at all stages, and, as the embryo differen- tiates from the anterior end of the primitive streak, the primitive pit must be regarded as moving back along the line of the primi- tive groove, always representing its anterior end. Sections. The preceding sketch of the superficial appearance of the primitive streak must now be followed by a careful exami- nation of its structure and role in the development. 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 Lillie, Frank Rattray, 1870-1947. New York, Holt
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