MY DEAR FRIEND AND HONORED COLLEAGUE:—Here I have been for two months in the basin of the Amazons, and it is here that I have heard with sorrow of the death of my old friend Valenciennes. I am the more affected by it, because no one would have appreciated more than he the results of my journey, which I had hoped soon to share with him. You will naturally understand that it is to the class of fishes I consecrate the better part of my time, and my harvest exceeds all my anticipations. You will judge of it by a few statements. On reaching Manaos, at the junction of the Rio Negro and the Amazons, I had already collected more than three hundred species of fishes, half of which have been painted from life, that is, from the fish swimming in a large glass tank before my artist. I am often pained to see how carelessly colored plates of these animals have been published. Not only have we tripled the number of species, but I count new genera by dozens, and I have five or six new families for the Amazons, and one allied to the Gobioides entirely new to Ichthyology. Among the small species especially I have found novelties. I have Characines of five or six centimetres and less, adorned with the most beautiful tints, Cyprinodonts resembling a little those of Cuba and the United States, Scomberesoces allied to the Belone of the Mediterranean, a considerable number of Carapoides, and Rays of different genera from those of the ocean, and therefore not species which ascend the river; and a crowd of Goniodonts and Chromides of unpublished genera and species. But what I appreciate most highly is the facility I have for studying the changes which all these fishes undergo with age and the differences of sex among them; which are often very considerable. Thus I have observed a species of Geophagus in which the male has a very conspicuous protuberance on the forehead, wholly wanting in the female and the young. This same fish has a most extraordinary mode of reproduction. The eggs pass, I know not how, into the mouth, the bottom of which is lined by them, between the inner appendages of the branchial arches, and especially into a pouch, formed by the upper pharyngials, which they completely fill. There they are hatched, and the little ones, freed from the egg-case, are developed until they are in a condition to provide for their own existence. I do not yet know how long this continues; but I have already met with specimens whose young had no longer any vitelline sac, but were still harbored by the progenitor. As I shall still pass a month at Teffé I hope to be able to complete this observation. The examination of the structure of a great number of Chromides has led me to perceive the affinities between these fishes and several other families with which we have never thought of associating them. In the first place, I have convinced myself that the Chromides, formerly