EXCURSIONS ON THE COAST. 383 



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 surprising, and cannot but have a direct influence 

 on the ideas now prevalent respecting 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, that 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. 



