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 distinctions 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 Linnaean 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, his trouble is increased tenfold. He must first 

 ascertain to which of the three great classes of ani- 

 mals, — the jRadiata, 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 



