Fig. 183. Musical apparatus of Cicada: a, moveable horny plate, drawn aside to display the plicated membrane; b, rings of the abdomen.

(934). All the luminous organs, both ventral and lateral, present essentially the same structure, consisting of an investing membrane enclosing a parenchyma composed of tracheae and nerves surrounding groups of cells so densely filled with white, spherical, minute granules, having an oily aspect when viewed by transmitted light, that no other constituent can be seen in them; and from experiments, as well as the anatomical facts, Kolliker concludes that the luminous organs are a nervous apparatus, whose nearest analogues are to be sought for in the electrical organs of certain fishes*.