. The development of the chick; an introduction to embryology. Birds -- Embryology. THE URIXOGEXITAL SYSTEM 399 this multiplication and the consequence is a great increase in thickness. At the same time the sexual cords cease to grow, and become converted into tubes with a wide lumen, and low epithelium; and the stroma increases notably in amount. The inner surface of the germinal epithelium, or ovigerous layer of the ovary, then begins to form low irregular projections into the stroma, or the latter begins to penetrate the ovigerous layer at irregular distances so as to produce elevations. Th
. The development of the chick; an introduction to embryology. Birds -- Embryology. THE URIXOGEXITAL SYSTEM 399 this multiplication and the consequence is a great increase in thickness. At the same time the sexual cords cease to grow, and become converted into tubes with a wide lumen, and low epithelium; and the stroma increases notably in amount. The inner surface of the germinal epithelium, or ovigerous layer of the ovary, then begins to form low irregular projections into the stroma, or the latter begins to penetrate the ovigerous layer at irregular distances so as to produce elevations. This condition is well illustrated in Fig. W^^^m^ germ £p. Fig. 229. — Cross-section of the ovary of a young embryo of Numenius arcuatus. (After Hoffmann.) bl. v., Blood-vessel, germ. Ep., Germinal epithelium, r., Mesonephric canals (rete ovarii), s. c, Sexual cord. In the course of development the ovigerous layer continually increases in thickness, and the projections into the stroma form veritable cords of ovigerous tissue, which correspond to the cords of Pfliiger in the mammalian ovary. The cords carry the primitive ova with them. The surface of the ovary also begins to become lobulated by the extension of the stroma tra- beculae. Successive stages in the growth and differentiation of the primitive ova occur from the surface towards the inner ends of the ovigerous strands. Fig. 230 represents a section through the ovary of a fledgling of Numenius acuatus three or four days. 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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