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 “ Regne 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 Linnaeus 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 which 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, Rcesel, 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 invertebrated animals. 
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