PRINCIPLES OP SCIENTIFIC ARRANGEMENT. 121 
Orders, Classes, Families, and Genera, all deduced 
in their successive and collateral groups from characters 
exclusively derived from species; therefore to the accu¬ 
rate knowledge of species all endeavours must be directed, 
they comprising within themselves all the rest, although 
the characters upon which they themselves depend for 
separation from their congeners are the most trivial of 
any. Each combination, in its analytical descent, con¬ 
tains characters of wider compass than those which suc¬ 
ceed it, and consequently embraces in that descent more 
species than the successive divisions ; just as in the ascent, 
or synthetical method, the characters of every successive 
group gradually expand. Species being thus the only 
real objects in nature from which all knowledge springs, 
and in which exclusively all uses lie, other combinations 
being perhaps as merely imaginary as are the many 
lines which are drawn over the surface of the globes, it 
would imply that subdivisions merely lend aid to ac¬ 
quire more rapidly the details upon which they depend. 
AVe will, therefore, first turn our attention to species. 
Both combination and subdivision are intended to 
facilitate identification, by aiding us to arrive at this 
knowledge of species; for each species represents a dis¬ 
tinct idea, whose correct definition is important to the 
progress of accurate science. This alone permits ob¬ 
servation to be attributed to its right object, and when 
properly recorded, the information is secured for ever 
from error or obscurity. It is not, however, the gift of 
every mind to discern accurately even specific differences, 
or to form skilfully generic combinations. The very best 
favoured by nature,—for it is a natural gift, although 
under high cultivation,—have sometimes a bias towards 
seeing more than actually exists. Hence varieties are 
