72 
INTRODUCTION. 
able to refer to the works treating of American species, 
so that he may ascertain whether his results have not 
been anticipated by others. And, if he would be worthy 
of entire confidence, he must not confine his observation 
to the cabinet. One who knows species only as they 
appear in his own drawers, can have but an imperfect 
idea of the innumerable deviations, from every type, 
that nature permits. Specimens iu cabinets are usually 
selected for their size, beauty, and perfection, or for 
some remarkable peculiarity about them, — those whose 
characters are strong and well defined, being always 
preferred, while the intermediate forms, a thousand 
times more numerous than the others, but presenting 
nothing notable, are neglected. The tendency to order 
and classification, which the study of Natural History 
creates, induces the in-door collector to separate and 
arrange his specimens according to their resemblances. 
With Ms materials he finds that distinctions are easily 
established, that the bounds of species and varieties are 
well defined, and that groups are marked by determinate 
and fixed characters. The limits of each division seem to 
him to be constant and not to encroach upon each other. 
As it is in his cabinet, so he supposes it to be in nature. 
He accordingly speculates, refines, and generalizes, and 
ends by establishing a system which, because consistent 
with his own experience, he thinks equally supported 
throughout. When the same person changes the scene 
of his observation from his own cabinet to the field and 
the forest, and becomes acquainted with numerous 
