228 MANUAL OF ZOOLOGY. 



no doubt can be entertained as to the reality of the relation- 

 ships between these two groups of animals. On the other 

 hand, many and close points of affinity unite the higher 

 Scoledda with the Ringed Worms (Annelida] ; and many syste- 

 matists unite the Scoledda and Anarthropoda in a common 

 sub-kingdom, to which they restrict the Linnean name of 

 Vermes. 



II. ANARTHROPODA. This division includes the Spoon 

 Worms (Gephyrea\ the Ringed Worms (Annelida), and the 

 Arrow Worms ( Chcetognathd), and is characterised by the fact 

 that the body is composed of a number (often indefinite) of 

 similar or nearly similar segments arranged longitudinally. A 

 " pseudo-haemal " system of vessels is generally present. The 

 nervous system is placed ventrally, and consists typically of 

 a double chain of ganglia, united by longitudinal commis- 

 sures, and forming an cesophageal collar. Cilia are generally 

 developed. Lateral locomotive appendages are usually pres- 

 ent, but are never jointed or articulated to the body. 



III. ARTHROPODA. This division includes the Crustaceans, 

 (Crustacea), the Spiders, Scorpions, &c. (Arachnida), the Cen- 

 tipedes and their allies (Myriapoda), and the Insects (Insecta). 

 The body (fig. r 1 2) is composed of a series (usually definite) 



Fig. 112. Diagram of the anatomy of an insect, an Antennae ; e Eye; m Mouth; 

 ^Gullet; sg Salivary gland ; * Stomach \f Tubes supposed to represent the kid- 

 neys ; z Intestine ; c Chamber (cloaca) into which the intestine opens ; v Vent ; 

 k Heart ; n Nervous system ; / Bases of the legs. 



of distinct rings or " somites," arranged along a longitudinal 

 axis. A true blood-vascular system is normally present, and 

 the heart is placed dorsally. The nervous system consists 

 primitively of a double chain of ganglia, placed ventrally, and 

 traversed anteriorly by the oesophagus. Limbs are almost 

 always present, and are jointed and articulated to the body. 

 The integument is more or less extensively hardened by the 

 deposition in it of chitine, with or without salts of lime ; and 

 ciliated epithelium is not developed. 



