ANNUL O SA. 



CHAPTER XXVIII. 



ANNULOSA. 



I, General Characters of Annulosa. 2. General 

 Characters of Anarthropoda. 3. Class Gephyrea. 

 4. General Characters of the Class Annelida. 



Sub-kingdom Annulosa. — The members of this sub-kingdom 

 are distinguished by the possession of a body which is composed 

 of numerous segments, or "somites^'' arranged along a longitudinal 

 axis. A nervous system is always present, and consists of a double 

 chain of ganglia, running along the ventral surface of the body, 

 and traversed anteriorly by the msophagus (fig. 54). The limbs 

 {when present) are turned towards the neural aspect of the body. 



The sub-kingdom Annulosa maybe divided into two primary 

 divisions, according as the body is provided with articulated 

 appendages, or not ; these divisions being termed respectively 



Fig. 54. — Diagram of an Annulose Animal, a Blood-vascular or hsmal system; 

 b Digestive system ; c Nenral system. 



the Arthropoda and Anarthropoda. The first of these com- 

 prises Crustaceans, Spiders, Scorpions, Centipedes, and Insects; 

 whilst the latter in,cludes the Spoon-worms, Leeches, Earth- 

 worms, Tube-worms, and Sand-worms. 



Division I. Anarthropoda. — In this division of the Annu- 

 losa the locomotive appendages are never distinctly jointed or arti- 

 culated to the body. In this division are included three classes, 

 viz. : — the Gephyrea, the Annelida, and the Chcetognatha. 



Class I. Gephyrea ( = Sipunculoidea). — This class includes 

 certain worm-like animals in which the body is sometimes ol^- 



