192 STUDY OF NATURAL HISTORY. 
thologist, and adopts an artificial arrangement, he 
finds that all birds are divided into two large groups— 
land and water birds —the distinetions of which, in 
ordinary cases, are immediately comprehended: but 
if he prefers a natural system, he has to peruse the 
characters of five or more primary groups, before 
he can refer his subject to one of these primary 
divisions. Should he, again, wish to understand the 
name of one of those soft slimy marine animals 
destitute of a shell, and of which nearly the whole 
of the Linnean class of Vermes, or worms, is com- 
posed, his labour will be still more abridged by 
using an artificial system. He turns to the Systema 
Natura, and he immediately finds that this animal 
will come under the order of Mollusca, concisely de- 
fined as “ naked simple animals, not included in a 
shell, but furnished with limbs.” Here, then, he 
looks no further, but proceeds at once to ascertain 
the genus, and possibly the species. Should he, 
however, wish to ascertain the natural group of his 
subject, histrouble is increased tenfold. He must first 
ascertain to which of the three great classes of ani- 
mals, —the Radiata, the Annulosa, and the Mollusca, 
it really belongs: and this, as the science now stands, 
will oblige him, in many cases, to dissect his subject; 
because each of these classes contains ‘naked simple 
animals, not included in a shell, but furnished with 
limbs.” From these examples, sufficient to illustrate 
the simplicity of a good artificial system, it will be 
immediately perceived how much the labour of any 
one who searches after names only, is abridged by 
the one method, and increased by the other. The 
truth is, that the perfection of an artificial system 

