8 A JOURNEY IN BRAZIL. 
in our mode of work, as compared with that of former 
investigators. When less was known of animals and plants 
the discovery of new species was the great object. This 
has been carried too far, and is now almost the lowest kind 
of scientific work. The discovery of a new species as such 
does not change a feature in the science of natural history, 
any more than the discovery of a new asteroid changes 
the character of the problems to be investigated by astrono- 
mers. It is merely adding to the enumeration of objects. 
We should look rather for the fundamental relations among 
animals ; the. number of species we may find is of impor- 
tance only so far as they explain the distribution and lim- 
itation of different genera and families, their relations to 
each other and to the physical conditions under which they 
live. Out of such investigations there looms up a deeper 
question for scientific men, the solution of which is to be 
the most important result of their work in coming genera- 
tions. The origin of life is the great question of the day. 
How did the organic world come to be as it is ? It must 
be our aim to throw some light on this subject by our pres- 
ent journey. How did Brazil come to be inhabited by the 
animals and plants now living there ? Who were its inhab- 
itants in past times ? What reason is there to believe that 
the present condition of things in this country is in any 
sense derived from the past ? The first step in this investi- 
gation must be to ascertain the geographical distribution 
of the present animals and plants. Suppose we first ex- 
amine the Rio San Francisco. The basin of this river is 
entirely isolated. Are its inhabitants, like its waters, com- 
pletely distinct from those of other basins ? Are its species 
peculiar to itself, and not repeated in any other river of 
the continent? Extraordinary as this result would seem, 
