. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. SIFHONAPTERA AND DIFTERA 375 mes I— already been stated, this part gives rise only to the mesoderm which by the deepening of the longitudinal ventral furrow later forms a tube (Figs. 328C, 329^). Escherich (1900) especially emphasized the point that the mesoderm near the anterior end of the embryo originates below the ectoderm as lateral diverticula of the gastral furrow (Fig. 329C), thus conforming wit
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. SIFHONAPTERA AND DIFTERA 375 mes I— already been stated, this part gives rise only to the mesoderm which by the deepening of the longitudinal ventral furrow later forms a tube (Figs. 328C, 329^). Escherich (1900) especially emphasized the point that the mesoderm near the anterior end of the embryo originates below the ectoderm as lateral diverticula of the gastral furrow (Fig. 329C), thus conforming with the mode of development exemplified by the Chaetognatha (Sagitta) (Fig. 40), except that in the muscid it is restricted to the posterior extremity of the very short anterior mid- gut rudiment, the middle strand being absent. The tube is first completed at the anterior and posterior ends. Anteriorly the invagination is complicated by the appearance of diverticula (Figs. 3295,C, 330). During this time, because of the growth of the embryo and the lengthening of the tubular mesoderm, the posterior mesenteron rudiment together with the germ cells is pushed over on the dorsal side (Figs. 329B,D). The transverse lines now deepen and extend around the egg. With the elongation of the tubular mesoderm these transverse furrows become displaced so that they occupy a more or less oblique position (Fig. S2SD). This is the only indication of rotation that is observable in the embryo of the muscids. The anterior converging folds now elongate still more as well as coming closer together, with the result that the anterior end of the germ band is more sharply defined. The original posterior transverse furrow which is now carried by the dorsad-growing posterior section of the germ band becomes more longi- tudinal in position, so that eventually it becomes a longitudinal furrow (Fig. 328D). The transverse lines which originally were found only on the ventral side now become more evident on the
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