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 232 EMBRYOLOGY OF INSECTS AND MYRIAPODS given off from the dorsal wall (Fig. 153, suboesb) increase in size and meet medially to form a cluster of cells that give rise to the subesophageal body. The other cells of the coelomic sacs form muscles. The first maxillary coelomic sacs have small rounded cavities (Figs. 152, 154), which do not develop a dorsal pouch but correspond to the ven-
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 232 EMBRYOLOGY OF INSECTS AND MYRIAPODS given off from the dorsal wall (Fig. 153, suboesb) increase in size and meet medially to form a cluster of cells that give rise to the subesophageal body. The other cells of the coelomic sacs form muscles. The first maxillary coelomic sacs have small rounded cavities (Figs. 152, 154), which do not develop a dorsal pouch but correspond to the ven- tral portion of other coelomic cavities. Their walls eventually develop into muscles of the first maxillae. The labial coelomic cavities (Fig. 152) first appear at 56 hours. They grow rapidly so that in the 70-hour stage they already show a long dorso- rostral and a short dorsoanal pouch. The ventral pouch fills the hollow ecf- Fig. 155.^—Locusta. Cross section of middle of second thoracic segment of 75-hour embryo, (am) Amnion, (bl) Blood cell, {coel) (1) Dorsorostal, (2) dorsoanal, (3) ventral pouch of coelomic sacs, (dc) Provisional dorsal closure, (ect) Ectoderm, (p) Second leg. of the second maxillary appendage and forms the labial musculature; the dorsorostral and anal portions contribute to the formation of the splanchnic mesoderm, the lateral myoblast plate, and the fat body. This is the largest of the gnathal coelomic sacs. The small mandibular and first maxillarj^ sacs correspond largely to the ventral portion of the labial coelom. The coelomic sacs of the thoracic segments (Figs. 147, 155, 156) develop in a similar manner appearing first in the hollow of their append- ages and lying obliquely to the long axis of the embryo. Their median, dorsoanterior ends are pointed, whereas the lateral, ventroposterior ends are rounded. In the 75-hour stage the coelomic sacs show three distinct pouches: the dorsorostral, the dorsoanal, and the ventral. The rostro- lateral coe
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