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 APTILOTA 177 From the time the chorion ruptures until after completed blasto- kinesis, 5 days have elapsed, or 10 days since the deposition of the eggs. The remaining steps in the development, the completion of body parts and organs until hatching, require on an average 10 more days, or a total of 20 days of incubation. During this final period of 10 days the number of
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 APTILOTA 177 From the time the chorion ruptures until after completed blasto- kinesis, 5 days have elapsed, or 10 days since the deposition of the eggs. The remaining steps in the development, the completion of body parts and organs until hatching, require on an average 10 more days, or a total of 20 days of incubation. During this final period of 10 days the number of simple eyes on each side increase to eight, and the appendages acquire the definitive number of segments: four for the antennae, five for the legs, and three for the fork. Mandibles and maxillae also increase in size (Fig. 88). The dorsal closure of the body is accomphshed by the growth of the ectoderm to replace the degenerating cells of the amnioserosa. The dorsal organ is taken into the alimentary canal at the time of the closure of the dorsal wall and digested with the remains of the yolk (Fig. 89). Shortly before emergence of the insect the dorsal organ as well as f ac Fig. 89.—Isotoma. Oblique, almost frontal section of thorax of late embryo. (,ac) Ali- mentary canal, (do) Dorsal organ. (/) Fatty tissue. the remains of the yolk have entirely disappeared from the ahmentary canal. The first evidence of digestive epithelium development is seen about 10 hours after egg deposition. This cellular layer originates from an anterior, a posterior, and a diffuse median anlage (Figs. 90, 91). Above the stomodaeum is a mass of cells which will give rise to the esophageal muscle (Fig. 90, mus). The apex of the stomodaeum is free from inner-layer cells. Below the stomodaeum (Fig. 90, mge) is another mass which will give rise to the anterior pair of rudiments of the mid-gut epithelium as well as muscles of the lower wall of the esophagus. A mass of inner-layer cells surrounds the t
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