EXCURSIONS ON THE COAST. 883 
the United States the collections accumulated, that our in- 
tended trip to the island of Marajo has been postponed day 
after day. Yesterday I witnessed a religious procession in 
two thousand.* But it is not only the number of species which will astonish, 
naturalists ; the fact that they are for the most part circumscribed within 
definite limits is still more surpi'ising, and cannot but have a direct influence 
on the ideas now prevalent respecting 1 the origin of living beings. That in a 
river like the Mississippi, which from the north to the south passes successively 
through cold, temperate, and warm zones, whose waters flow sometimes over 
one geological formation, sometimes over another, and across plains covered 
at the north by an almost arctic vegetation, and at the south by a sub-tropical 
flora, I hat in such a basin aquatic animals of different species should be met 
at various points of its course is easily understood by those who are ac- 
customed to consider general conditions of existence, and of climate especially, 
as the first cause of the difference between animals and plants inhabiting sepa- 
rate localities. But that from Tabatinga to Para, in a river where the waters 
differ neither in temperature nor in the nature of their bed, nor in the vegeta- 
tion along their borders, that under such circumstances there should be met, 
from distance to distance, assemblages of fishes completely distinct from each 
other, is indeed astonishing. I would even say that henceforth this distribution, 
which may be verified by any one who cares to take the trouble, must throw 
much doubt on the opinion which attributes the diversity of living beings to 
local influences. Another side of this subject, still more -curious perhaps, is the 
intensity with which life is manifested in these waters. All the rivers of 
Europe united, from the Tagus to the Volga, do not nourish one hundred and 
fifty species of fresh-water fishes ; and yet, in a little lake near Manaos, called 
Lago Hyanuary, the surface of which covers hardly four or five hundred 
square yards, we have discovered more than two hundred distinct species, the 
greater part of which have not been observed elsewhere. What a contrast ! 
The study of the mixture of human races in this region has also occupied 
me much, and I have procured numerous photographs of all the types which 
I have been able to observe. The principal result at which I have arrived is, 
that the races bear themselves towards each other as do distinct species ; that is 
to say, that the hybrids, which spring from the crossing of men of different 
* To-day I cannot give a more precise account of the final result of my 
survey. Though all my collections are safely stored in the Museum, every 
practical zoologist understands that a critical examination of more than eighty 
thousand specimens cannot be made in less than several years. L. A. 
