. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 82 EMBRYOLOGY OF INSECTS AND MYRIAPODS ently has made a similar suggestion for Sciara coprophila. More work on late embryonic and early larval stages is necessary for convincing proof of the origin of this membrane in Diptera. As has been described in the foregoing chapter, the origin of the mid-gut epithelium has been the source of much controversy. What- ever may be its origin, among the Hymenoptera and D
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 82 EMBRYOLOGY OF INSECTS AND MYRIAPODS ently has made a similar suggestion for Sciara coprophila. More work on late embryonic and early larval stages is necessary for convincing proof of the origin of this membrane in Diptera. As has been described in the foregoing chapter, the origin of the mid-gut epithelium has been the source of much controversy. What- ever may be its origin, among the Hymenoptera and Diptera, as well as some Coleoptera, Lepidoptera, etc., at each extremity of the inner (lower) layer, either united with it or contiguous to it, a cell mass, or. mge proct mgs Fig. 44.—Sagittal section of embryo. Development of mid-gut epithelium, {am) Amnion, {br) Brain, (ggl) Ganglion, {mge and mgs) Mid-gut epithelium, (proct) Proctodaeum. (stom) Stomodaeum. mesenteron rudiment (mge), is developed, which by many is regarded as an entoderm derivative. From each of these two cell masses or rudi- ments two ribbons (rb) of cells grow out, those from the anterior mass growing posteriorly, those from the posterior mass growing anteriorly, until their tips meet (Figs. 43, 44). After fusion of their tips the ribbons (rb) widen until they wholly enclose the yolk. The ribbons usually arise from the ventrolateral angles. In some cases, only a single middorsal ribbon arises from each cell mass; in others instead of a ribbon each rudiment develops in the form of a cup, one covering each end of the yolk, the rims of the cups facing each other and finally fusing. In some insects, in addition to the two ribbons, cells liberated from the middle strand of the inner layer contribute toward building the 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 pe
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