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 MYRIAPODA 399 Below the base of the cells that are to form the retinal and the nerve- fiber cells (Fig. 355, rt) flattened cells {en. c) appear from which the envelope cells will arise. The delicate radiating plasma processes {rhd) of the retinal cells develop into the visual rods. The cells that are mingled with the plasma-process bearing retinal cells now draw down in contact with the
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 MYRIAPODA 399 Below the base of the cells that are to form the retinal and the nerve- fiber cells (Fig. 355, rt) flattened cells {en. c) appear from which the envelope cells will arise. The delicate radiating plasma processes {rhd) of the retinal cells develop into the visual rods. The cells that are mingled with the plasma-process bearing retinal cells now draw down in contact with the eye-envelope cells and become fusiform nerve fibers. Thus the undifferentiated cells marked 'ri' in Fig. 355 differentiate into retinal and nerve-fiber cells. The optic nerve appears to originate from a prominence (op. n) at the proximal end of the eye anlage, the nerve therefore growing inward to meet the optic lobe rather than growing outward from it. The optic lobe and the eye recede from each other, Fig. 355.—Scolopendra cingulata. Section through anlage of eye. {hi) Blood cell. (6sm) Basement membrane, {cut) Cuticula. {ect) Ectoderm, (en. c) Envelope cell. {gglc) Ganglion cell. {It) Lentigene cell. {op. n) Proximal end of optic nerve, {pr. gglc) Proliferation center of optic ganglion, {rhd) Rhabdome. {rt) Retinal cell. {Adapted from Heymons.) but the connection between them remains. When the embryo enters the so-called 'fetal stage,' having shed the chorion and thrown off the embryonic cuticula, the first pigment granules may be seen. Soon the corneagene (lentigene) cells, which surround the periphery of the eye (It), grow over the eye surface and proceed to secrete a delicate cuticula, which is continuous with that of the adjacent body wall. The sub- sequent development of the eye is postembryonic and may be briefly described as follows: Fig. 356 represents the eye of an adult centipede. Before a molt takes place, the corneagene cells (It), which normally form iris-
Size: 1772px × 1129px
Photo credit: © Bookworm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
