. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 298 EMBRYOLOGY OF INSECTS AND MYRIAPODS still exists in the yolk, but by this time the chromatin material has disintegrated almost entirely (Fig. 239). The cleavage nuclei in the area nearest this last remnant of the polar body are not so numerous as in other regions of the periphery, and no cell walls have begun to form, although they are well along in development on the opposite side of the egg. This woul
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. 298 EMBRYOLOGY OF INSECTS AND MYRIAPODS still exists in the yolk, but by this time the chromatin material has disintegrated almost entirely (Fig. 239). The cleavage nuclei in the area nearest this last remnant of the polar body are not so numerous as in other regions of the periphery, and no cell walls have begun to form, although they are well along in development on the opposite side of the egg. This would indicate that as long as the polar body lasts, its presence prevents the cleavage nuclei from entering the periphery. The oosome is an irregular mass of granular material located at the posterior pole of the egg. When stained with either iron haemo- toxylin or Delafield's haemotoxylin it appears much darker than the nb / ^ '' ''â '>"'' ^>- '^^?o to"-"* ''W^% ""^^^ ^^ ^^^ cytoplasm of the egg. ^^ * '^â ^''â '' "" â '-^^ i^ j^^y form a saucer-shaped disk lying between the yolk and the cytoplasm (Fig. 234) or a smaller but very thick mass extending for some distance into the yolk (Fig. 235). In either case it is not homogeneous but contains large globules or irregular bodies of mate- rial which stain much lighter and appear to be identical in composi- tion with the peripheral cytoplasm. Yolk globules also are scattered through the germinal cytoplasm but not to the same extent as the Fig 2iO-Brachyrh^nus Longitudinal Ughter staining material, section of blastoderm {bid). {gc) Germ cells. As they approach the posterior (pb) Polar body. p^j^^ ^^^^ ^f ^^le cleavage nuclei come into contact with the germinal cytoplasm (oosome) which breaks up and gathers around them in large masses. They move on to the periphery but do not leave the walls of the forming blastoderm (Fig. 239). They are the germ cells, and their development from this poin
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