. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 14 EMBRYOLOGY OF INSECTS AND MYRIAPODS cases begin in the middle and extend caudally and finally to the head end. The invaginated part is in the form of a tube which later flattens, obliter-. "^""^ neurg ^ Fig. 14.—Cross section of germ band after completion of serosa {aer). {am) Amnion. () Amniotic cavity, (ect) Ectoderm, (il) Inner layer, {neur) Neuroblasts. {neurg) Neural groov
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 14 EMBRYOLOGY OF INSECTS AND MYRIAPODS cases begin in the middle and extend caudally and finally to the head end. The invaginated part is in the form of a tube which later flattens, obliter-. "^""^ neurg ^ Fig. 14.—Cross section of germ band after completion of serosa {aer). {am) Amnion. () Amniotic cavity, (ect) Ectoderm, (il) Inner layer, {neur) Neuroblasts. {neurg) Neural groove, (yc) Yolk cell, (ysp) Yolk spherule. ating the cavity (Figs. 13, 14). The flattened tube represents the inner (or so-called ''lower") layer which differen- tiates into a median, or middle, strand which ends anteriorly and posteriorly in a cell mass (the so-called "secondary entoderm") and the two lateral mesoderm bands. To what extent we are justified in considering the longitudinal furrow as a gastrular invagi- nation and in regarding the inner laj^er as composed of a middle entoderm strand and two lateral mesoderm bands is discussed in Chap. VI of this text. Blastokinesis, Segmentation of the Em- bryo, and Formation of Appendages.—When the lateral and anterior amniotic folds have formed, the embryo pushes still further into the yolk. This shift in position with respect to the yolk and change in length is termed "blastokinesis" (Fig. 12). Meanwhile there may now be recognized, first, the protocephalon, , the cephalic lobes of the embryo comprising the labrum, eyes, antennae, and usually the postoral somite of the second antennae; and, second, the protocorm, or the remaining part of the embryo. Later segmentation occurs, 6 segments eventually forming in the head, 3 in the thorax, and 11 in the abdomen with a telson in Please note that these images are extracted from scanned page images that may have been digitally enhanced for read
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