ANNELIDES. 127 



DIVISION III. ARTICULATA. 



THE third great division of the Animal Kingdom consists 

 of animals which have their body or members composed of seg- 

 ments or articulated rings, to the interior of which the mus- 

 cles are attached. The nervous system consists of two long 

 chords extending along the belly, and swelled out at intervals into 

 knots or ganglia. The first of these, placed upon the oesopha- 

 gus, though but little larger than the others, is considered as 

 analogous to the brain in the higher animals. The teguments 

 of the body are sometimes hard, sometimes soft ; and the trunk 

 has often at its sides articulated members, though in some 

 groups these are wanting. As formerly observed, it is in this 

 division of the Animal Kingdom that the transition of the cir- 

 culation in closed vessels to nutrition by imbibition is observed ; 

 and the corresponding transition from respiration in circumscrib- 

 ed organs, to that performed by trachea or air-vessels distri- 

 buted through the body. The organs of movement and of sense 

 are disposed symmetrically on the sides of a common axis. The 

 senses of taste and sight seem the most distinct; and their jaws, 

 when they have any, are always lateral. This division of the 

 Animal Kingdom contains five classes, viz. ANNELIDES, CRUS- 

 TACEA, ARACHNIDES, MYRIAPODA, and INSECTA. 



CLASS V. ANNELIDES. 



Body soft, more or less elongated, naked or inclosed in a tube, 

 and divided into a number of segments ; blood red. 



THE animals of this class are the only invertebral ones which 

 have red blood circulating in a double system of complicated 

 vessels. Their body is naked or inclosed in a tube, formed of 

 segments, or transversley wrinkled, and often without a head, 

 eyes, or antennae. They are destitute of articulated feet ; but 

 the greater portion have in their place setiferous retractile pa- 

 pillae disposed in lateral rows. The mouth is nearly terminal 



