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 214 EMBRYOLOGY OF INSECTS AND MYRIAPODS ceph to form the serosa. The inner layer, or, as Cholodkovvsky (1891) terms it, the primary ''entoderm,' is formed by a feeble invagination followed by delamination, proliferation, and migration. At the cephalic end the inner layer divides to underlie the cephalic lobes which have been formed by lateral proliferation of the germ band. The amnion 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 214 EMBRYOLOGY OF INSECTS AND MYRIAPODS ceph to form the serosa. The inner layer, or, as Cholodkovvsky (1891) terms it, the primary ''entoderm,' is formed by a feeble invagination followed by delamination, proliferation, and migration. At the cephalic end the inner layer divides to underlie the cephalic lobes which have been formed by lateral proliferation of the germ band. The amnion forms in a normal way (Fig. 129), the tail fold appearing first (Fig. 130). Segmentation is not evident until the rudiments of the appendages are well developed. Riley (1904) recognized six head segments: the ocular (preoral), antennal, second antennal (premandibular), mandibular, maxillary, and second maxillary (labial). The leg rudiments lie folded beneath the thorax and the anterior part of the abdomen. The rudimentary appendages of the abdomen disappear about six days after fertilization, except the pair on the first segment which persists until the envelopes rupture. The segments, as also the appendages, develop from the cephalic toward the posterior end. With the lengthening of the embryo the caudal end folds over ventrally (Fig. 131), and then the embryo shifts to a more posterior position (Fig. 132). Mean- while, further lengthening pushes the head forward until it reaches the cephalic end of the egg. With this increase in length the amnion and serosa tear longitudinally along the mid-ventral line, the amnion reflecting back although maintaining its connection with the margin of the embryo, the serosa contracting until both amnion and serosa are drawn into the yolk on the dorsal side in the prothoracic region. While the remains of the envelopes are gathering on the dorsal side, the lateral parts of the body wall grow upward to enclose the yolk. The dorsal growth of the b
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