VOYAGE FROM NEW YORK TO RIO DE JANEIRO. 9 
I nevertheless expect to find it so. The next water-basin 
we shall have to examine will be that of the Amazons, 
which connects through the Rio Negro with the Orinoco. 
It has been frequently repeated that the same species of 
fish exist in the waters of the San Francisco and in those 
of Guiana and of the Amazons. At all events, our works 
on fishes constantly indicate Brazil and Guiana as the 
common home of many species ; but this observation has 
never been made with sufficient accuracy to merit confi- 
dence. Fifty years ago the exact locality from which 
any animal came seemed an unimportant fact in its sci- 
entific history, for the bearing of this question on that 
of origin was not then perceived. To say that any speci- 
men came from South America was quite enough ; to 
specify that it came from Brazil, from the Amazons, the 
San Francisco, or the La Plata, seemed a marvellous accu- 
racy in the observers. In the museum at Paris, for instance, 
there are many specimens entered as coming from New 
York or from Para ; but all that is absolutely known about 
them is that they were shipped from those sea-ports. Nobody 
knows exactly where they were collected. So there are 
specimens entered as coming from the Rio San Francisco, 
but it is by no means sure that they came exclusively from 
that water-basin. All this kind of investigation is far too 
loose for our present object. Our work must be done with 
much more precision ; it must tell something positive of 
the geographical distribution of animals in Brazil. There- 
fore, my young friends who come with me on this expedi- 
tion, let us be careful that every specimen has a label, 
recording locality and date, so secured that it shall reach 
Cambridge safely. It would be still better to attach two 
labels to each specimen, so that, if any mischance happens 
