. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. NEUROPTERA AND COLEOPTERA 291 cells, which arise later from the tip of the stomodaeal invagination and which will surround a portion of the yolk somewhat as in the Odonata, may then be designated as the secondary entoderm. The embryo elongates and at the same time decreases in diameter in the dorsoventral direction (Fig. 225). A lower layer develops diffusely without the formation of a gastrula furrow (Fig.
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. NEUROPTERA AND COLEOPTERA 291 cells, which arise later from the tip of the stomodaeal invagination and which will surround a portion of the yolk somewhat as in the Odonata, may then be designated as the secondary entoderm. The embryo elongates and at the same time decreases in diameter in the dorsoventral direction (Fig. 225). A lower layer develops diffusely without the formation of a gastrula furrow (Fig. 226); the head (antr) and tail end (post) are at this time differentiated, the former less thickened than the latter. The amnion-like envelope becomes progressively thinner; the yolk, owing apparently to pressure, becomes longer and thinner. At this stage one observes in the amniotic cavity small struc- tureless masses which stain differently from adjacent cells (Fig. 226, par). •oos\. anir Fig. 227.—Siylops nycthemerae. (am) Amnion, {antr) Anterior, (post) Poste- rior end. (vent) Venter, (y) Yolk. anir. 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 Johannsen, O. A. (Oskar Augustus), 1870-1961; Butt, Ferdinand Hinckley, 1899-. New York, London, McGraw-Hill Book Company, inc.
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