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 OLIGOENTOMATA AND APT I LOT A 169 surface of the embryo (Fig. 72). At the time the chorion ruptures, the second cuticle {cut 2) of the embryo also loosens to form the second crenated membrane of Claypole (1898). After the chorion has ruptured, it is apparent that the embryonic rudiment (germ band) forms a belt around the yolk, the head and tail ends nearly meeting at the dorsal organ (F
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 OLIGOENTOMATA AND APT I LOT A 169 surface of the embryo (Fig. 72). At the time the chorion ruptures, the second cuticle {cut 2) of the embryo also loosens to form the second crenated membrane of Claypole (1898). After the chorion has ruptured, it is apparent that the embryonic rudiment (germ band) forms a belt around the yolk, the head and tail ends nearly meeting at the dorsal organ (Fig. 72). The cells of the germ band are columnar and two-layered, the outer forming the ectoderm; the inner, the inner layer. The cells of the original blastula which lie on the sides of the egg have become flattened and thinner and have lost Fig. 72.—Isotoma. Rupture of chorion {ch). {cut 1, cut 2) First and second crenated membranes, (gc) Germ cells. (M) Head lobes. the inner-layer cells which have migrated into the inner layer of the germ band (Figs. 73, 74). According to Uzel, the germ band of Campodea is formed in a similar manner. Since the flattened cells on the sides together with the germ band form an envelope covering the yolk, and since they are a part of the original blastula, these flattened cells may be called the 'amnioserosa.' The germ band now shows distinct head lobes (Fig. 76, hi), a broad tail lobe, and four body segments. After the rupture of the chorion, which takes place about five days after egg deposi- tion, the dorsal organ takes on another character. The cells themselves retain their previous appearance, with vacuolate inner and a fibrillar outer part, but are more expanded with the outer fibrillar part projecting
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