. Elements of comparative anatomy. Anatomy, Comparative. 35G COMPARATIVE ANATOMY. cartilage of tlie iris (ik). Outside and behind this optic capsule is the ganglion of the optic nerve, in the periphery of which there is a whitish organ (w) which projects more or less forwards. Behind this there is a longitudinal layer of muscles, and lastly, a silvery membrane (argentea externa) (ae), which reaches as far as the edge of the pupil, and invests the bulb on its inner face, or the one turned towards the above-mentioned cavity. Internally to it there is the argentea interna. The bundles of nerves w
. Elements of comparative anatomy. Anatomy, Comparative. 35G COMPARATIVE ANATOMY. cartilage of tlie iris (ik). Outside and behind this optic capsule is the ganglion of the optic nerve, in the periphery of which there is a whitish organ (w) which projects more or less forwards. Behind this there is a longitudinal layer of muscles, and lastly, a silvery membrane (argentea externa) (ae), which reaches as far as the edge of the pupil, and invests the bulb on its inner face, or the one turned towards the above-mentioned cavity. Internally to it there is the argentea interna. The bundles of nerves which arise from the ganglion (<jo) behind the cartilaginous cap- sule, pass to the retina by a large number of pores in it; the retina lies within the cartilaginous capsule, and is con- tinued forwards as far as the edge of an organ which carries the lens. This retina is formed of essentially the same layers as the same portion of the eye of the Gastropoda; an internal (Bi) portion, which contains the perceptive apparatus, is separated from the external part (Be) by a layer of pigment (P). A layer of connec- tive tissue extends inwards to the lens (L) from the layer of muscular fibres; this completely separates the eye into two parts, an anterior smaller and a posterior larger one; these unite to form an oval body, the long axis of which corresponds to the optic axis. There are epithelial thickenings on the anterior, as well as on the posterior, surface of this layer of connective tissue; they unite to form a system of lamellas, which invests the edge of the lens, and is known as the " ciliary body " (ci) (corpus epitheliale). The cavity behind the lens is filled up by a fluid. Hensen, Zeitschr. f. wiss. Zool. Bd. XV. [Lankestek, E. Kay, Develt. of Cephalopoda. Quart. Journ. Microsc. Sci. 1875.] Auditory Organs. § 274. It is possible, apparently, to derive the organs, which seem to be auditory in the Mollusca, from the vesicles or otocysts which we met with iu the
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
