. Coleoptera : general introduction and Cicindelidae and Paussidae. Fig. 15.—Diagrammatic section of the eye of a beetle, au, facetted eye;c, transparent cornea made up of numerous lenses (cl); Jc, layer ofcrystalline cones concealed by pigment; rh, rt, rhabdoms and retinulse,partly concealed by pigment; nbs, nervous structures; go, globularapex of the optic nerve; no, optic nerve; tr, two tracheae belongingto the optic nerve; or, part of the chitinous orbit of the eye. (AfterKolbe.) is only found in the imago of a few species, and then in conjunctionwith the compound eye (as in Omalium, etc.)
. Coleoptera : general introduction and Cicindelidae and Paussidae. Fig. 15.—Diagrammatic section of the eye of a beetle, au, facetted eye;c, transparent cornea made up of numerous lenses (cl); Jc, layer ofcrystalline cones concealed by pigment; rh, rt, rhabdoms and retinulse,partly concealed by pigment; nbs, nervous structures; go, globularapex of the optic nerve; no, optic nerve; tr, two tracheae belongingto the optic nerve; or, part of the chitinous orbit of the eye. (AfterKolbe.) is only found in the imago of a few species, and then in conjunctionwith the compound eye (as in Omalium, etc.). Some of the cave- 22 INTRODUCTION. frequenting beetles (as Anillus), are blind, and only possess quiterudimentary organs of vision. The compound facetted eye is one of the most intricateand wonderful structures in the whole animal kingdom. Each facet is the outside coveringor cornea of an elongate andcomplex apparatus called an om-matidium (fig. 16), each consistingof a corneal or crystalline lens (cor.),under which comes the crystallinecone {con.), which is borne on a rod-like structure or rhabdom (r.) ;,underneath the rhabdoms is foundthe basal or fenestrated membrane(), which is backed by a mass ofnerves ; these latter penetrate themembrane and run up into the spacebetween the rhabdoms. Accordingto Sharp and others the penetrating-nerve have their distal extremitiesconnected with the delicate sheaths,by one of which each rhabdom is sur-rounded, the combination of sheathand nerves forming a zones or layers of pigment arepresent, one, in which the pigmentcells are shorter, enclosing the chiefpart
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbeetles, bookyear1912
