LEAVE MANAOS. 



347 



last, hardly two months intervened, while those made on 

 our first arrival at Manaos in September up to the present 

 time cover an interval of four months ; from the first to 

 the last at Yilla Bella more than five months will have 

 elapsed. On this account I attach great importance to the 

 renewal of my investigations at that place, as well as to 

 the later collections from Obydos, Santarem, Monte Alegre, 

 Porto do Moz, Gurupa, Tajapuru, and Para. As far as 

 these comparisons have gone, they show that the distinct 

 faunae of the above-named localities are not the result of 

 migrations ; for not only have different fishes been found 

 in all these basins at the same time, but at different times 

 the same fishes have been found to recur in the same basins, 

 whenever the fishing was carried on, not merely in favored 

 localities, but as far as possible over the whole area indis- 

 criminately, in deep and shoal waters. Should it prove that 

 at Pard,, as well as at the intervening stations, after an in- 

 terval of six months, the fishes are throughout the same as 

 when we ascended the river, the evidence against the sup- 

 posed extensive migrations of the Amazonian fishes will 

 certainly be very strong. The striking limitation of species 

 within definite areas does not, however, exclude the presence 

 of certain kinds of fish simultaneously throughout the whole 

 Amazonian basin. The Pirarucu, for instance, is found 

 everywhere from Peru to Par4 ; and so are a few other 

 species more or less extensively distributed over what may 

 be considered distinct ichthyological faunae. But these wide- 

 spread species are not migratory ; they have normally and 

 permanently a wide range, just as some terrestrial animals 

 have an almost cosmopolite character, while others are cir- 

 cumscribed within comparatively narrow limits. Though 

 most quadrupeds of the United States, for instance, differ 



