SUPPLEMENT ON CRUSTACEA. 227 



basis of his first partitions, the presence or absence of wings, 

 he placed them at the end of this class, in the order aptera, 

 of which they compose, with the palpous arachnida, the second* 

 division. His opinion was generally followed. But Brisson, 

 in his '^' Re gne Animal,^' continued to distinguish the Crustacea 

 from the insects, placed them immediately after the fish, and 

 associated with them the arachnida and myriapoda. His 

 Crustacea, therefore, are all the insects of Linngeus which have 

 more than six feet. The apterous order of the Swedish natu- 

 ralist subsequently underwent some modifications, but it pre- 

 served the same rank in all the methods w'hich were established 

 on the same principles. 



Fabricius at first composed with the Crustacea his fourth 

 order of insects, that of agonata, which he thus named because 

 they have no under lip. In this order he placed the scor- 

 pions, and removed the onisci and monoculi of Linnaeus. 



No regard was paid, in these and other methodical distri- 

 butions, to the essential differences presented by the internal 

 structure of these animals, although some great naturalists, 

 such as Swammerdam, Roesel, and Degeer, had already ob- 

 served a circulation and gills in the Crustacea ; and though it 

 was easy to conclude from hence, that their organization dif- 

 fered from that of insects, and approximated more to that of 

 superior animals, it was reserved for the first naturalist of 

 onr age, whom it is unnecessary to name, to awaken our atten- 

 tion to this most important point, and to direct our steps into 

 the true road to a natural classification. At first, in his Ele- 

 mentary View of the Natural History of Animals, founded 

 upon such considerations, he transported the Crustacea to the 

 head of the insect class, and formed with them a special and 

 well-circumscribed division. Soon after, in his Comparative 

 Anatomy, he made a peculiar class of the Crustacea ; and his 

 example was followed at the same time by M. de Lamarck, in 

 his public lectures on the invertebratcd animals, 



Q 2 



