entering the electric battery arise from the same cerebral region, and now I have found that the pouch in which the egg of the Acara is incubated and its young nursed for a time, receives its nerves from the same source. This series of facts is truly wonderful, and only shows how far our science still is from an apprehension of the functions of the nervous system.—L. A. Footnote 71: It is a very general habit among the South American Indians to pierce the nose, ears, and lips with holes, in which they hang pieces of wood and feathers, as ornaments. Footnote 72: See “Expeditions into the Valley of the Amazons,” published by the Hakluyt Society. Footnote 73: This species belongs to one of the subdivisions of the genus Auchenipterus; it is undescribed, and Mr. Burkhardt has made five colored sketches of a number of specimens of different sizes, varying in their markings.—L. A. Footnote 74: When I attempted to record my impression of the basin of the Amazons, and characterized it as a fresh-water ocean with an archipelago of islands, I did not mean to limit the comparison to the wide expanse of water and the large number of islands. The resemblance extends much further, and the whole basin may be said to be oceanic also, in the character of its fauna. It is true, we are accustomed to consider the Chromides, the Characines, the Siluroids, and the Goniodonts, which constitute the chief population of this network of rivers, as fresh-water fishes; but in so doing we shut our eyes to their natural affinities, and remember only the medium in which they live. Let any one enter upon a more searching comparison, and he will not fail to perceive that, under the name of Chromides, fishes are united which in their form and general appearance recall several families of the class, only known as inhabitants of the sea. The genus Pterophyllum, for instance, might be placed side by side with the Chætodonts, without apparently violating its natural affinities, since even Cuvier considered it as a Platax. The genera Symphysodon and Uaru would not seem very much out of place, by the side of Brama. The genus Geophagus and allied forms recall at once the Sparoids, with which some of them were associated by earlier ichthyologists; while the genus Crenicichla forms a striking counterpart to the genus Malacanthus. Finally, the genus Acara and their kindred closely resemble the Pomacentroids. Indeed, had not the fresh-water genera Pomotis, Centrarchus, and the like, been erroneously associated with the Percoids, the intimate relations which bind them to the Chromides, and these again to the marine types mentioned above, would long ago have been acknowledged. The genus Monocirrus is a miniature Toxotes, with a barbel. Polycentrus, which is also found in the Amazons, stands nearest to Acara and Heros; it has only a larger number of anal spines. In this