[56]. Afterwards I made a longer stay at Monte Alégre, and learned to know its picturesque nooks and dells, where a luxuriant vegetation is watered by delicious springs. I feel that the above description is superficial; but I let it remain, as perfectly true to my first impressions.
[57]. I soon became convinced after leaving Pará that the faunæ of our different stations were not repetitions of each other. On the contrary, at Breves, Tajapurú, Gurupá,—in short, at each stopping-place, as has been seen,—we found another set of inhabitants in the river, if not wholly different from the last, at least presenting so many new species that the combination was no longer the same. It became at once very important to ascertain whether these differences were permanent and stationary, or were, in part at least, an effect of migration. I therefore determined to distribute our forces in such a way as to keep collecting parties at distant points, and to repeat collections from the same localities at different seasons. I pursued this method of investigation during our whole stay in the Amazons, dividing the party for the first time at Santarem, where Messrs. Dexter, James, and Talisman separated from us to ascend the Tapajoz, while Mr. Bourget remained at Santarem, and I, with the rest of my companions, kept on to Obydos and Villa Bella.—L. A.
[58]. I was especially interested in seeing living Gymnotini. I do not here allude to the electric Gymnotus, already so fully described by Humboldt that nothing remains to be said about it; but to the smaller representatives of that curious family, known as Carapus, Sternopygus, Sternarchus and Rhamphichthys. The Carapus, called Sarapos throughout Brazil, are very numerous, and the most lively of the whole group. Their motions are winding and rapid like those of the Eel, but yet different, inasmuch as they do not glide quickly forward, but, like Cobitis and Petromyzon, turn frequent somersets and change their direction constantly. This is also the case with the Sternopygus and Sternarchus, and even the larger and more slender Rhamphichthys have a kind of rolling motion. Though I had expected to find many Cyprinodonts, yet their great variety astonished me, and still more was I struck by their resemblance to Melanura, Umbra, and the Erythrinoids. The presence of Belone and allied forms also surprised me. Our stay on the shores of José Assú and Lago Maximo was particularly instructive on account of the numerous specimens of each species daily brought in by Laudigári and Maia. It afforded me a welcome opportunity for studying the differences exhibited by these fishes at different periods of life. No type passes, in that respect, through greater changes than the Chromides, and among them the genus Cychla is perhaps the most variable. I am sure that no ichthyologist could at first sight believe that their young are really the early stage of the forms known in our ichthyological works as Cychla monocolus, Cychla temensis, and Cychla saxatilis. The males and females also vary greatly during the spawning season, and the hump on the top of the head described as a specific character in Cychla nigro-maculata is a protuberance only found in the male, swelling during the period of spawning and soon disappearing. Once familiar with the young brood of some species of Chromides, it became easy for me to distinguish a great variety of small types, no doubt hitherto overlooked by naturalists travelling in this region, simply under the impression that they must be the young of larger species. A similar investigation of the young of Serrasalmo, Myletes, Tetragonopterus, Cynodon, Anodus, &c. led me to the discovery of an equally large number of diminutive types of Characines, many of which, when full grown, do not exceed one inch in length; among them are some of the most beautiful fishes I have ever seen, so far as the brilliancy and variety of their colors are concerned. Thus everything contributed to swell the collections,—the localities selected as well as the mode of investigating. I should add here, that, several years before my own journey on the Amazons, I had been indebted to the Rev. Mr. Fletcher for a valuable collection of fishes from this and other Amazonian localities. The familiarity thus obtained with them was very useful to me in pursuing my studies on the spot.—L. A.
[59]. As will be seen hereafter, want of time and the engrossing character of his work in the Amazons, compelled Mr. Agassiz to renounce the journey into Peru, as also the ascent of the river Madeira.
[60].
To His Excellency M. Couto de Magalhaēs, President of Pará.
My dear Sir:—I thank you sincerely for the kind letter you were so good as to write me last week, and I hasten to inform you of the extraordinary success which continues to crown our efforts. It is certain from this time forth, that the number of fishes inhabiting the Amazons greatly exceeds all that has hitherto been imagined, and that their distribution is very limited on the whole, though a small number of species have followed us since we left Pará and others have a range more or less extensive. You remember, perhaps, that, when alluding to my hopes, I told you one day that I believed in the possibility of finding from two hundred and fifty to three hundred species of fish in the whole basin of the Amazons; even now, having passed over less than one third of the main stream, and only diverged here and there to some points beyond its shores, I have already obtained more than three hundred. It is incredible, above all, if one considers that the total number known to naturalists does not reach one third of what I have already collected. This result scarcely allows one to foresee the discoveries to be made whenever the affluents of the great river are explored with the same care. An exploration of the Araguay for its whole course, in order to teach us how many different combinations of distinct species occur in succession, from its sources to its junction with the Tocantins and lower down till it meets the Amazons, would be an enterprise worthy of you. You have already a sort of scientific property in this river, to which you would add new rights in furnishing science with this information.
Permit me to express to you all the gratitude I feel for the interest you take in my young travelling companion. Mr. Ward is worthy of it, alike from his youth, his courage, and his devotion to science. Mr. Epaminondas has just communicated to me your generous intentions towards myself, and your purpose of sending a steamer to Manaos to take the place of the Piraja, and facilitate our exploration of the Rio Negro and the Rio Madeira. I do not know how to thank you enough; all that I can say is, that this favor will allow me to make an exploration of these rivers which would be otherwise impossible. If the result of these researches be as favorable as my hopes, the honor will be due, in the first instance, to the liberality of the Brazilian government. Encouraged by the results thus far obtained, I think that, if the circumstances are favorable, on arriving at Tabatinga, we shall make a push into the lower part of Peru, while my companions will explore the rivers intermediate between this town and Teffé; so that we shall probably not return to Manaos before the end of October.
Accept, my dear Sir, the assurance of my high regard, &c., &c.
L. Agassiz.