Note 69 — Chapter VII · LIFE IN TEFFÉ.

Teffé, September 22, 1865.

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from those of the ocean, and therefore not species which ascend the river; and a crowd of Goniodonts and Chromides of unpublished genera and species.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 scattered among the Labroides and the Sciænoids, really constitute a natural group recognized nearly at the same time and in an independent manner by Heckel and J. Müller. But, beside these, there are the genera Enoplosus, Pomotis, Centrarchus, and some other neighboring genera, classed among the Percoids by all Ichthyologists, which seem to me, from this distance and without means of direct comparison, so near the Chromides that I do not see how they can be separated, especially now that I know the lower pharyngials not to be invariably soldered in the Chromides. And then the embryology and metamorphoses of the Chromides, which I have just been studying, have convinced me that the fishes with labyrinthic branchiæ, separated from all other fishes by Cuvier, as a family entirely isolated on account of the strange structure of its respiratory organs, are closely related to the Chromides. Thus this group becomes, by its various affinities, one of the most interesting of the class of fishes, and the basin of the Amazons seems to be the true home of this family. I will not fatigue you with my ichthyological researches; let me only add, that the fishes are not uniformly spread over this great basin. I have already acquired the certainty that we must distinguish several ichthyological faunæ very clearly characterized. Thus the species inhabiting the river of Pará, from the borders of the sea to the mouth of the Tocantins, differ from those which are met in the network of anastomoses uniting the river of Pará with the Amazons proper. The species of the Amazons below the Xingu differ from those which occur higher up; those of the lower course of the Xingu differ from those of the lower course of the Tapajoz. Those of the numerous igarapés and lakes of Manaos differ as much from those of the principal course of the great river and of its great affluents. It remains now to study the changes which may take place in this distribution in the course of the year, according to the height of the waters, and perhaps also according to the epoch at which the different species lay their eggs. Thus far I have met but a small number of species having a very extensive area of distribution. One of those is the Sudis gigas, found almost everywhere. It is the most important fish of the river, that which, as food, corresponds to cattle for the population along the banks. Another problem to be solved is, how far this phenomenon of the local distribution of fishes is repeated in the great affluents of the Amazons. I shall try to solve it in ascending the Rio Negro and Rio Madeira, and as I return to Manaos I shall be able to compare my first observations in this locality with those of another season of the year. Adieu, my dear friend. Remember me to M. Elie de Beaumont and to those of my colleagues of the Academy who are interested in my present studies. My kind remembrance also to your son.

Always yours,

L. Agassiz.