. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. OLIGONEPHRIDIA 265 daeum, and that the gut suspensorium alone is derived from the secondary entoderm. The account and figures given by Hirschler of the development of the embryonic envelopes are not so clear as those given by Will (1888) for Aphis pelargonii. In A. pelargonii, at the place where the serosa joins the amnion (Fig. 188-B) and where the serosa joins the head lobe, the amniotic fold (Fig. 188D,
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. OLIGONEPHRIDIA 265 daeum, and that the gut suspensorium alone is derived from the secondary entoderm. The account and figures given by Hirschler of the development of the embryonic envelopes are not so clear as those given by Will (1888) for Aphis pelargonii. In A. pelargonii, at the place where the serosa joins the amnion (Fig. 188-B) and where the serosa joins the head lobe, the amniotic fold (Fig. 188D, amf) will appear. This fold is two-walled at the base (Fig. 188£',a), but beyond this point the amnion fuses with the serosa into a single membrane which continues around the head lobe to form what Will has designated as the "cephalic-serosa" (Figs. 1S8E; 189, ser. ceph). The structure thus differs in that only the serosa covers the head instead of both amnion and serosa as in many insects. The other later processes of development—the rupture of the cephalic embiyonic envelope, the evagination of the embryo through the opening. (bid) Blasto- Ovarian yolk (mycetom). (yc) Yolk cells. Fig. 191.—Toxoptera. {bid) Blasto- derm. ((/) Primary yolk, {y 2) Ova- rian yolk (mycetom). {yc) Yolk cells. thus produced, and the rotation of the germ band—occur in the same way as described for the Libellulidae. The Egg of the Oviparous Sexual Generation.—The modes of develop- ment described above apply to the viviparous parthenogenetic summer generations of aphids. Since the development of the oviparous sexual winter generation differs in some particulars, a brief abstract of the account of Webster and Philhps (1912) of the embryology of the stem mother of the grain aphid {Toxoptera graminum) will serve as an example. The eggs are broadly elhpsoidal, with a slight reniform tendency. At oviposition they are pale yellow, changing in a few hours to a faint greenish color, some day
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