. The elasmobranch fishes . C D Fig. 233. Sagittal section of eye. (From Franz.) A. Acanthias. B. CetorJdnus. C. Spinax. D. Raja iatis. ah., space for aqueous humor; c, ciliary body; ch., choroid coat; en., cornea; ir., iris; I., lens; , lens muscle; , optic pedicel; r., retina; sc, sclerotic coat; sJ., dorsal suspen- sory ligament; sch., suprachoroidea; //, optic nerve. The eyelids are movable in only a few Elasmobranchs. In Scyllium, while they are so sluggish as rarely to close, yet the eye has been observed to bat. In many other forms the lids are more or less completely devoid of
. The elasmobranch fishes . C D Fig. 233. Sagittal section of eye. (From Franz.) A. Acanthias. B. CetorJdnus. C. Spinax. D. Raja iatis. ah., space for aqueous humor; c, ciliary body; ch., choroid coat; en., cornea; ir., iris; I., lens; , lens muscle; , optic pedicel; r., retina; sc, sclerotic coat; sJ., dorsal suspen- sory ligament; sch., suprachoroidea; //, optic nerve. The eyelids are movable in only a few Elasmobranchs. In Scyllium, while they are so sluggish as rarely to close, yet the eye has been observed to bat. In many other forms the lids are more or less completely devoid of musculature and are therefore immovable. In others musculature may be fairly well de- veloped (see p. 104, fig. 106). In the rays the eyes are firmly fixed so that movement is impossible. Structure op Adult Eye The structure of the adult eye in a number of Elasmobranchs has been studied in detail by Franz (1905). In a median sagittal section through the eye of Acanthias striking the optic pedicel (fig. 238a) the various structures making up the eye appear. In the anterior part is the clear cornea (en.) and extending almost against it is the spherical crystalline lens (I.). The clear space between the two (aJi.) is filled with aqueous humor. The dark layer {ir., fig. 233c) is the pigmented iris, a circular curtain which contains the color of the eye; the
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