344 



A JOURNEY IN BRAZIL. 



la, 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 Ama- 

 zons 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 end- 

 less diversity of fishes he now knows to exist in this im- 

 mense 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 investiga- 

 tions 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, con- 

 sisting 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 



