AKTHROPODA. 91 



or two rows, but sometimes absent. The females are largest, and 

 are oviparous or ovoviparous. The respiratory, digestive, and 

 nervous systems closely resemble those of the larvae of insects. 



Fossil species are found as early as the Carboniferous epoch. 



The species of this class are known as gaily worms and centi- 

 pedes. For Latreille they formed the first order of insects. 



Body segmented. 



One pair of legs to each somite CHILOPODA. 



Two pairs of legs to each somite CHILOGNATHA. 



Body unsegmented MALACOPODA. 



Order I. CHILOGNATHA. 



DlPLOPODA. 



Body more or less cylindrical and crustaceous. No foot-jaws. 

 Antennae of rarely more than seren joints. Two pairs of legs to 

 each somite, except the first five or six. 



The mandibles are without palpi ; the second pair of gnathites 

 (maxillae) are united to form a lower lip. The number of somites 

 varies from nine to eighty. 



These are sluggish animals, living on decomposing animal and 

 vegetable matter, and laying in the earth a great number of eggs. 

 Glomeridae are capable of rolling themselves into a ball. Poly- 

 zoniidaa are the Siphonizantia or Sugentia of Brandt. 



A minute centipede, Pouroptts Huxleyi, in its earliest stage with 

 three pairs of legs, gradually increasing with each moult to nine 

 pairs, was discovered by Sir J. Lubbock in Kent. He considers 

 it the "connecting-link between Chilognatha and Chilopoda ; 

 Packard places it between Myriopoda and Collembola. Claus 

 puts it with Polyxenida3. It differs from all other Myriopoda 

 in having no tracheoa, and also in having bifid antennae. Another 

 species is found in !Xorth America. 



