. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. HYMENOPTERA 317 producing male broods. The history of cleavage as well as of the embry- onic cells is the same in fertilized and unfertilized eggs. The freshly deposited egg is a pear-shaped cell, surrounded by a thin but tough membrane (Fig. 265) and averaging mm. in length. The nucleus {nu) is near its anterior end. In fertilization the sperm enters the Fig. 268. Fig. 269. Fig. 265.—Litomastix
. Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching. Embryology -- Insects; Embryology -- Myriapoda. HYMENOPTERA 317 producing male broods. The history of cleavage as well as of the embry- onic cells is the same in fertilized and unfertilized eggs. The freshly deposited egg is a pear-shaped cell, surrounded by a thin but tough membrane (Fig. 265) and averaging mm. in length. The nucleus {nu) is near its anterior end. In fertilization the sperm enters the Fig. 268. Fig. 269. Fig. 265.—Litomastix. Fertilized egg. {os) Oosome. {nu) Nucleus, (sp) Sperm. Fig. 266.—Litomastix. Fertilized egg after second maturation division. (^1) Outer nucleus of first polar body. (A2) Inner nucleus of first polar body. (51) Second polar body nucleus. (B2) Female pronucleus, {os) Oosome. (sp) Sperm. Fig. 267.—Litomastix. (Al) Outer nucleus of first polar body. (52) Female pronucleus. {nu. p) Polar nucleus ( = A2 + 51). {os) Oosome. {sp) Sperm. Fig. 268.—Litomastix. With two cleavage nuclei. {Al) and () First polar bodies. (51) Second polar body, {nu) Cleavage nuclei, (os) 05some. Fig. 269.—Litomastix. Two-cell stage. (Al) First polar body nucleus, {nu. p) Polar nucleus, {nu) Cleavage nucleus, {os) Oosome. egg at any point on the surface of the posterior region. Polyspermy never occurs. Within the egg is the oosome ("germ-line determinant"), a nucleolus-like body (os). Maturation is identical in fertihzed and unfertilized eggs. The first maturation division results in reducing the number of chromosomes from sixteen to eight. The second division, but without reduction, follows immediately upon the first or may even precede it (Fig. 2QQA1,A2,B1). The result of these two divisions is the formation of three polar bodies (A1,A2,B1) and the ootid (B2), the latter forming the female Please note that these images are extracted from scanned page images that may ha
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