SIRE:—On arriving here this morning I had the most agreeable and unexpected surprise. The first fish brought to me was the Acara, which your Majesty kindly permitted me to dedicate to you, and by an unlooked-for good fortune it was the breeding season, and it had its mouth full of little young ones in the process of development. Here, then, is the most incredible fact in embryology fully confirmed, and it remains for me only to study, in detail and at leisure, all the changes which the young undergo up to the moment when they leave their singular nest, in order that I may publish a complete account of this curious history. My anticipations as to the distribution of fishes are confirmed; the river is inhabited by several very distinct ichthyological faunæ, which have, as a common link, only a very small number of species to be met with everywhere. It remains now to ascertain with precision the limits of these ichthyological regions, and I may perhaps be drawn on to devote some time to this study, if I find the means of accomplishing it. There is a question which now becomes very interesting; it is to know how far the same phenomenon is reproduced in each one of the great affluents of the river Amazons, or, in other words, whether the fishes of the upper regions of the Rio Madeira, the Rio Negro, &c., &c., are the same as those of the lower course of these rivers. As to the diversity of fishes in the whole basin, my expectations are far surpassed. Before arriving at Manaos I had already collected more than three hundred species, that is to say, at least three times the number of species thus far known. About half have been painted from life by Mr. Burkhardt; if I can succeed in publishing all these documents, the information I shall be able to furnish on this subject will exceed all that has been thus far made known. I should be very glad to learn that your Majesty has not met with difficulties on the voyage, and has been able fully to accomplish the ends proposed. We are here without news from the South since we left Rio, and all we had learned then was, that after a very stormy passage your Majesty had reached the Rio Grande. May God protect and bless your Majesty! With sentiments of the most profound respect and the liveliest gratitude, I am Your Majesty’s very humble and obedient servant, L. AGASSIZ. Footnote 66: