ANARTHROPODA. 119 



toward that side of tte body upon which the nervous system 

 is situated, (See also the transverse section of an Annulose 

 animal, Fig. 1.) The entire sub-kingdom of the Annulosa is 

 divided into two great divisions termed Arthropoda and 

 Anarthropoda, according as the body is provided with jointed 

 appendages or not. In the Arthropoda, in which the body- 

 rings are furnished (some or all) with jointed appendages, are 

 included the Crustaceans (lobsters, crabs, etc.), the spiders and 

 scorpions, the centipedes, and the insects. In the Anarthro- 

 poda, in which there are no true jointed appendages, are in- 

 cluded the spoon-worms, leeches, earth-worms, tube-worms, 

 and sand-worms.* 



Division I. Anaetheopoda (Gr. a, without ; arthros, joint ; 

 podes, feet). — In this division of the Annulosa, the locomotive 

 appendages are never distinctly jointed or articulated to the 

 body. In this division are included two principal classes — the 

 Gephyrea and the Annelida. \ 



Class I. Gephteea. — This class is a very small one, and 

 includes a number of worm-like animals, which in most re- 

 spects are very similar to the following class of the Annelida, 

 but are distinguished by having no locomotive appendages at- 

 tached to the sides of the body. They were long placed among 



Fig. 45. — Gephyrea. Sijrinx nudus (after Torbes). 



the Echinodermata, having a decided relationship to the worm- 

 like Solothurians. They are distinguished, however, by never 

 secreting calcareous matter in the skin, and by having no 

 water-vascular or ambulacral system. There can be no doubt, 



* The Anarthr&poda are often united with the ScoUcida into a common Bub-kingdom 

 under the name of V&rmes; in which case the EcMnod&nnata are retained apart in a 

 Bpecial sub-kingdom. 



+ A third class has been constituted under the name of Clwdognatha for some singular 

 marine animals, transparent and worm-Uke in form, with lateral fins at the hinder end of the 

 body, and having the mouth armed with bristles. They form the genus Sagitta. 



