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 Fig. 51.—Adaptive ocellus of Acilius larva. (n) Nerve, {ret) Retina, {rod) Cuticxilar rods. {x) Retinal cells bordering slit. {From Patten.) {ep) Epidermis. {I) Rudiment of lens. {si) Slit in retina, {vit) Vitreous body. account of the development of these structures in the embryo of Acilius, one of the water beetles, has shown that the later developmental stages occur after hatching. I
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 Fig. 51.—Adaptive ocellus of Acilius larva. (n) Nerve, {ret) Retina, {rod) Cuticxilar rods. {x) Retinal cells bordering slit. {From Patten.) {ep) Epidermis. {I) Rudiment of lens. {si) Slit in retina, {vit) Vitreous body. account of the development of these structures in the embryo of Acilius, one of the water beetles, has shown that the later developmental stages occur after hatching. In the larva of Acilius there are three pairs of stemmata on each side which differ more or less from one another in structure. The ventral stemma of the third pair, being somewhat typical, will be described here. The rudiment, which at an early stage reminds one of the cup-shaped eyes of some mollusks, consists of a simple pit-like depression in a thickened part of the epidermis (Fig. 51A). The deep cells which form the wall of the pit and which are continuous with the thinner adjacent body wall (ep) are arranged in a single layer. The distal end of the elongate cells have a cuticular margin (rod) and at their inner ends give off nerve fibers which unite to form the optic nerve (n). Before this stage is reached the larva has emerged from the egg. Subsequently, the eye pit closes toward the exterior (Fig. 51B), the epidermal marginal parts pushing toward the center of the pit until they meet. Thus an eye cup is formed which is two-layered, the central part of the outer layer (vit) becoming the lenticular layer or vitreous body, while the
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