. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 308 EMBRYOLOGY OF INSECTS AND MYRIAPODS The mid-gut ribbons apparently develop from the ends of the stomo- daeum and proctodaeum. They extend beneath the yolk and grow- posteriorly and anteriorly until they meet and fuse. As they lengthen they also widen out, eventually closing in under the yolk to form a trough. On the sixth day they are already well developed but have not met along stom. Fig. 257.—Brachyr
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 308 EMBRYOLOGY OF INSECTS AND MYRIAPODS The mid-gut ribbons apparently develop from the ends of the stomo- daeum and proctodaeum. They extend beneath the yolk and grow- posteriorly and anteriorly until they meet and fuse. As they lengthen they also widen out, eventually closing in under the yolk to form a trough. On the sixth day they are already well developed but have not met along stom. Fig. 257.—Brachyrhinus. Sagittal section of ten-day embryo. i]br) Brain, {h) Heart, (rreffg) Mid-gut epithelium, (nc) Nerve cord. (procO Proctodaeum. (s«om) Stomodaeum- (x) Loop of mid-gut. the mid-ventral longitudinal line (Fig. 251). Two days later the trough of the mid-gut is completed ventrally, and the embryo has grown more than halfway around the yolk toward the dorsal side (Fig. 256). The dorsal wall of the mid-gut and the dorsal wall of the ectoderm are completed at the same time. For several days the mid-gut walls appar- ently continue to grow, for in an embryo shortly before hatching there appears a fold on the ventral side of the mid-gut that extends deeply into the yolk (Fig. 257).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Johannsen, O. A. (Oskar Augustus), 1870-1961; Butt, Ferdinand Hinckley, 1899-. New York, London, McGraw-Hill Book Company, inc.
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