Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . of the Pigment Membrane of the Choroid Coat, highly magni-fied.—It is seen to consist of regular six-sided plates, the tissue of which is filled withgrains of coloring matter. Figure 8. Compound Eyes of the Bee, highly magnified, showing the Division into Facets, and also the Conical Shape of each separate Portion.—A, Facets still more highlymagnified. B, The s^me with hairs growing between them. Figure
Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . of the Pigment Membrane of the Choroid Coat, highly magni-fied.—It is seen to consist of regular six-sided plates, the tissue of which is filled withgrains of coloring matter. Figure 8. Compound Eyes of the Bee, highly magnified, showing the Division into Facets, and also the Conical Shape of each separate Portion.—A, Facets still more highlymagnified. B, The s^me with hairs growing between them. Figure 9. A, Frcnt View of the Crystalline Lens. Figure 10. Side View of the Crystalline Lens.—a, Its anterior and least convexity. b, Its posterior and greatest convexity. Figure 11. The Crystalline Lens, after being immersed in boiling water.—The lines on its surface show its division into three parts. Figure 12. The Three Segments of the Crystalline Lens.—The faces of the segments show the concentric layers of which it is composed (like the coats of an onion). Thonucleus, or central portion of the lens, is seen on one of the segments, and on thitwo are corresponding Fid II Fig. 12 ? THE SENSES. 175 366. Most insects are furnished with compound eyes,which consist of several hexagonal facets, {Jig. 8, Pl. XIV.)united together in such a manner as to form a large, dark-colored protuberance on each side of the head. Each ofthese facets is an eye in itself. In some insects, thesefacets are exceedingly numerous. In the eye of a butter-fly, 17,000 have been counted; in some species of beetle,25,000; in the common horse-fly, 4,000. These numer-ous eyes, no two of which have the same direction, seemto compensate for the inability of the insects to move thehead without moving the whole body, since they are pro-vided with an eye in every direction. 367. Spiders are furnished with from six to fourteeneyes, situated on the most prominent part of the back,instead of on th
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