Embryology of insects and myriapods; Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching embryologyofinse00joha Year: 1941 Fig. 102.—Campodea. Section of egg with entoderm cells (e?ii). irregular layers of nuclei (Fig. 100). From all parts of the surface, nuclei migrate toward the margin of the thicker area, with the result that the upper two-thirds of the blastoderm loses most of its nuclei and the lower third gains them (Fig. 101). Nuclei then leave the center of the thick- ened area and pile up on the si
Embryology of insects and myriapods; Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching embryologyofinse00joha Year: 1941 Fig. 102.—Campodea. Section of egg with entoderm cells (e?ii). irregular layers of nuclei (Fig. 100). From all parts of the surface, nuclei migrate toward the margin of the thicker area, with the result that the upper two-thirds of the blastoderm loses most of its nuclei and the lower third gains them (Fig. 101). Nuclei then leave the center of the thick- ened area and pile up on the sides, leaving but a single layer in the center (Fig. 102). Occasional cells come to lie above on the inner side of the ent—^* ent-^ X \ I iG 103 —Campodea. Sec tion ot egg with mesodeiin tells (mes) (ent) EntoJoiin. ^ Fig. 104.—Campodea. Section of (aw. ser) Amnioserosa. (eci) Ectoderm. (ent) Entoderm, (mes) Mesoderm. thickened ring of cells. These are the future entoderm cells (Fig. 102, ent). Another migration of nuclei then takes place, reducing the thick- ness of the ring wall and restoring nuclei to the upper part of the egg as well as to the center of the ring (Fig. 103). The cells that increase in number in the center of the ring later give rise to the mesoderm (mes).
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