. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 598 ANIMAL PHYSIOLOGY. rudiments of our eyes. Among invertebrates, eyes may in gen- eral be divided into two classes: 1. The compound or faceted eyes, the structure of which may be gathered from the accom- panying figures. It will be noted that in such the retina is con- vex, and is made up of large compound nerve-rods (retinulcB), separated from one another by pigment-sheaths. The picture. Fia. 439. Fio. 440. Fio. 439.—Diagrammatic representation
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 598 ANIMAL PHYSIOLOGY. rudiments of our eyes. Among invertebrates, eyes may in gen- eral be divided into two classes: 1. The compound or faceted eyes, the structure of which may be gathered from the accom- panying figures. It will be noted that in such the retina is con- vex, and is made up of large compound nerve-rods (retinulcB), separated from one another by pigment-sheaths. The picture. Fia. 439. Fio. 440. Fio. 439.—Diagrammatic representation of compound eye in an Arthropod (after Glaus). C, cornea ; K, crystalline lens ; P, pigment; R, nerve-rods of retina; Fb, layer of fibers; Gz, layer of ganglion cells ; Bf, retinal fibers; Fk, crossing of fibers. Fie. 440.—Tliree facets with retinulae from compound eye of cockchafer (after Grenacher). Pigment has been dissolved away from two of the facets. F, corneal facet; K, cirstaUine cone; P, pigment-sheath; P', chief pigment-cell; P", pigment-cells of second order; S, retiniUae. formed by such eyes must represent a sort of mosaic, and be rather deficient in definition and brightness. It will be noticed that in such eyes, both the cornea and crystalline lens of verte- brates are represented in multiple form. This form of eye is found in crustaceans and some insects. 2. The simple eye pre- vails among annelids, insects, arachnids, moUusks, and verte- brates. A more advanced form of such a visual organ is found in the cuttle-fish. It may be seen (Fig. 443) that such an eye corresponds fairly well with the eye of a vertebrate. The eye of the fish is characterized by flatness of the cornea;. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mills, Wesley, 1847-1915. New York, D. Appleton
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