At the end of this week we resume our voyage on board the “Ibicuhy,” going slowly down to Pará, stopping at several points on the way. Our first station will be at Villa Bella, where Mr. Agassiz wishes to make another collection of fishes. It may seem strange that, after having obtained, nearly five months ago, very large collections from the Amazons itself at this point, as well as from the lakes in the neighborhood, he should return to the same locality, instead of choosing another region for investigation. Were his object merely or mainly to become acquainted with the endless diversity of fishes he now knows to exist in this immense fresh-water basin, such a repetition of specimens from the same locality would certainly be superfluous, since it is probable that a different point would be more prolific in new species. The mere accumulation of species is, however, entirely subordinate to the object which he has kept in view ever since he began his present researches, namely, that of ascertaining by direct observation the geographical range of the fishes, and determining whether their migrations are so frequent and extensive as they are said to be. I make an extract from Mr. Agassiz’s notes on this subject. “I have been frequently told here that the fishes were very nomadic, the same place being occupied at different seasons of the year by different species. My own investigations have led me to believe that these reports are founded on imperfect observations, and that the localization of species is more distinct and permanent in these waters than has been supposed; their migrations being, indeed, very limited, consisting chiefly in rovings from shallower to deeper waters, and from these to shoals again, at those seasons when the range of the shore in the same water-basin is affected by the rise and fall of the river;—that is to say, the fishes found at the bottom of a lake covering perhaps a square mile in extent, when the waters are lowest, will appear near the shores of the same lake when, at the season of high waters, it extends over a much wider area. In the same way, fishes which gather near the mouth of a rivulet, at the time of low waters, will be found as high as its origin at the period of high waters; while fishes which inhabit the larger igarapés on the sides of the Amazons when they are swollen by the rise of the river, may be found in the Amazons itself when the stream is low. There is not a single fish known to ascend from the sea to the higher courses of the Amazons at certain seasons, and to return regularly to the ocean. There is no fish here corresponding to the salmon, for instance, which ascends the streams of Europe and North America to deposit its spawn in the cool head-waters of the larger rivers, and then returns to the sea. The wanderings of the Amazonian fishes are rather a result of the alternate widening and contracting of their range by the rise and fall of the waters, than of a migratory