_December 6th._—Manaos. Mr. Thayer returned to-day from Lake Alexo, bringing a valuable collection of fish, obtained with some difficulty on account of the height of water; it is rapidly rising now, and the fish are in consequence daily scattered over a wider space. This addition with the collections brought in by Mr. Bourget and Mr. Thayer from Cudajas, by Mr. James from Manacapuru, and by Major Coutinho from Lake Hyanuary, José-Fernandez, Curupira, &c., &c., brings the number of Amazonian species up to something over thirteen hundred. Mr. Agassiz still carries out his plan of dispersing his working force in such a manner as to determine the limits of the distribution of species; to ascertain, for instance, whether those which are in the Amazons at one season may be in the Solimoens at another or at the same time, and also whether those which are found about Manaos extend higher up in the Rio Negro. For this reason, as we have seen, while at Teffé himself he kept parties above in various localities,—at Tabatinga and on the rivers Iça and Hyutahy; and now, while he and some of his assistants are collecting in the immediate neighborhood of Manaos, Mr. Dexter and Mr. Talisman are on the Rio Negro and Rio Branco. Following the same plan in descending the river, he intends to establish one station at Serpa, another at Obydos, another at Santarem, while he will go himself to the river Mauhes, which connects the Amazons with the Madeira. _December 10th._—To-day Mr. Dexter and Mr. Talisman returned from their canoe excursion to the Rio Branco. They are rather disappointed in the result of their expedition, having found the state of the waters most extraordinary for the season and very unfavorable for their purpose. The Rio Negro was so full that the beaches had entirely disappeared, and it was impossible to draw the nets; while on the Rio Branco the people stated that the water had not fallen during the whole year,—an unheard-of phenomenon, and unfortunate for the inhabitants, who were dreading famine for want of their usual supply of dried and salted fish, on which they so largely depend for food. This provision is always made when the waters are lowest, and when the large fish, driven into shallower and narrower basins, are easily caught. Though their collection of fish is therefore small, including only twenty-eight new species, Mr. Dexter and Mr. Talisman bring several monkeys, a very large alligator, some beautiful birds, among them the blue Mackaw, and a number of very fine palms. To-morrow we leave Manaos in the Ibicuhy, on an excursion to the little town of Mauhes, where we are to pass a week or ten days. Though we return for a day or two on our way to the Rio Negro, yet we feel that our permanent stay in Manaos is over. The six weeks we have passed here have been very valuable in scientific results. Not only has Mr. Agassiz largely increased his knowledge of the fishes, but he has had an opportunity of accumulating a mass of new and