774 ARTICULATA—ANNELIDES. 
DIVISION AlIP—ARTICULATA. 
Tue third great division of the animal kingdom consists of animais whicn 
have their body or members composed of segments or articulated rings, te 
the interior of which the muscles are attached. The nervous system con- 
sists of two long chords extending along the belly, and swelled out at inter- 
vals into knots or ganglia. The first of these placed upon the wsophagus, 
tnough but little larger than the others, is considered as analogous to the 
orain in the higher animals. The teguments of the body are sometimes 
hard, sometimes soft; and the trunk has often at its sides articulated mems 
bers, though in some groups these are wanting. As formerly observed, it is 
in this division of the animal kingdom, that the transition of the circulation 
in closed vessels to nutrition by imbibition is observed ; and the correspond- 
ing transition from respiration in circumscribed organs, to that performed 
by trachea, or air vessels distributed through thé body. The organs of 
movement and sense are disposed symmetrically on the sides of a common 
axis. The senses of taste and sight seem most distinct; and their jaws, 
when they have any, is always lateral. This division of the animal kingdom 
contains five classes, Viz :--ANNELIDES, CRUSTACEA, ARACHNIDES, MYRIAPODA, 
and INSECTA. 
CLASS V._ANNEGI DES, 
Body soft, more or less elongated, naked or inclosed in a tube, and divided vnto 
a number of segments; blood red. 
‘ 
THE animals of this vlass are the only invertebral ones which have red 
blood, circulating in a double system of complicated vessels. Their body is 
naked or inciosed in a tube, formed of segments, or transversely wrinkled, 
and often without a head, eyes, or antenne. They are destitute of articu- 
iated feet ; but the greater portion have in their place, setiferous, retractile 
rapille disposed in lateral rows. The mouth is nearly terminal simple, 
erpicular, or labiated, or in the form of a maxillary proboscis. The anatomis 
cal structure of the animals of this class has been investigated by Cuvier, 
Montegre, Spix, and Savigny; and the result of their observations has led to 
their arrangement in a separate group. The animals of this group, it may 
be remarked, formed part of the class Vermes, of Linnzus. 
The head of these species which are provided with one, is a slight anterior 
thickening, distinct from the first segments of the body, and upon which are the 
antenne and eyes. The antenne are articulated filaments, sometimes short 
and thick, inserted on the head, and of which the number exceeds five. 
The eyes, to the number of two or four, are also upon the head, behind the 
