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 mes mes mes Fig. 340.—Scolopendra cingulata. Cross sections A, B, successive stages, {hi) Blood cell, (dm) Membrana dorsalis. {ent) Entoderm cell, {mes) Mesoderm, {vm) Mem- brana ventralis. {y) Yolk, {yc) Yolk cell. {Adapted from Heymons.) germ disk becomes dispersed, migrating forward as two lateral mesoderm bands of cells. Meanwhile the ectodermal layer, except on the median line w
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 mes mes mes Fig. 340.—Scolopendra cingulata. Cross sections A, B, successive stages, {hi) Blood cell, (dm) Membrana dorsalis. {ent) Entoderm cell, {mes) Mesoderm, {vm) Mem- brana ventralis. {y) Yolk, {yc) Yolk cell. {Adapted from Heymons.) germ disk becomes dispersed, migrating forward as two lateral mesoderm bands of cells. Meanwhile the ectodermal layer, except on the median line which is now but one cell layer in thickness, gives rise to additional ectodermal cells by radial cell division and mesodermal cells by tangential division (delamination), the latter not encroaching on the median line (Fig. 340A). The occasional isolated cells found on the median line below the ectoderm are doubtless undifferentiated entoderm and mesen- chyme cells, but the cells that are later found between the two lateral mesoderm bands appear to develop into blood cells. The entoderm cells, in contrast to the mesoderm cells, become somewhat flattened and attach themselves to the yolk surface (Fig. 340B). A median longitudi- nal furrow or invagination is not formed in the germ band.
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