The elasmobranch fishes (1934) The elasmobranch fishes elasmobranchfish03dani Year: 1934 Fig. 244. Longitudinal section of lateral sensory canal, Mustelus canis. (From S. E. Johnson.) Grp., neuroniasts; CJvi., nerve; , lateral sensory canal; HmJ., ramus of lateral nerve; , primary hair cell; Sim., supporting cells; Tub., tubule to exterior. canals the lumen is flattened; but in the ventral canals it is rounded. On the median wall of the canal the section passes through a sense organ or neuro- mast, composed of cells derived from the basal layer of epidermis (). These are of two
The elasmobranch fishes (1934) The elasmobranch fishes elasmobranchfish03dani Year: 1934 Fig. 244. Longitudinal section of lateral sensory canal, Mustelus canis. (From S. E. Johnson.) Grp., neuroniasts; CJvi., nerve; , lateral sensory canal; HmJ., ramus of lateral nerve; , primary hair cell; Sim., supporting cells; Tub., tubule to exterior. canals the lumen is flattened; but in the ventral canals it is rounded. On the median wall of the canal the section passes through a sense organ or neuro- mast, composed of cells derived from the basal layer of epidermis (). These are of two types, one a crescentic supporting cell and the other an elongated club-shaped sense cell. A longitudinal section through the lateral sensory canal of Mustelus canis (fig. 244) by Johnson (1917) shows that the neuro- niasts are much more numerous than are the tubes {Tub.) which open to the surface. Each of these groups {Grp.) is composed of primary hair cells {), secondary sense cells at the sides of the primary cells, and under- lying these the supporting cells. Innervation of the lateral line in the body is by means of the lateral division of the vagus or tenth cranial nerve. It will be observed from figure 244 that the ramuli {Rml.) reach the canal at about the position of the tubules, but that they break up into numerous fibers, which supply a multitude of neuroniasts {Grp.). In the most anterior part of the lateral line canal, however, a few twigs are received from the ramus dorsalis X {, fig. 245) and the supra- temporalis X. Other twigs of the supratemporalis X supply the supratemporal canal. The segment of the lateral canal immediately anterior to the supratem-
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