MYRIOPODA. 



5 8l 



which belong to the thorax and those which are referable to the 

 abdomen. The post-cephalic segments, with the exception of the 

 last, usually carry a single pair of jointed legs each. Among the 

 living Myriopods, Pauropus has only nine pairs of legs ; but, with 

 this exception, eleven pairs of legs is the smallest number possessed 

 by any existing type. In the Millepedes (Diplopodd) each apparent 

 segment carries two pairs of legs (fig. 437); but this is really due to 



Fig. 436. — Lithobius forjicatus, 

 a recent Centipede, enlarged, and 

 viewed dorsally. an, Antennae ; 

 h, Head ; /, Foot-jaw. 



Fig. 437. — lulus 

 maximus, a re- 

 cent Millepede. 



the coalescence of the somites in pairs, each apparent segment being 

 in reality composed of two amalgamated somites. 



In the abnormal genus Pauropus respiration is cutaneous, but in 

 all other living Myriopods the breathing-organs are in the form of 

 " tracheae " — that is to say, tubes which open on the surface of the 

 body by minute apertures or " stigmata," and which convey the air 

 into the interior of the body. In Peripatus the tracheae open ex- 

 ternally by irregularly placed " stigmata " over the whole surface of 

 the body. In the Centipedes the " stigmata " are placed on the 

 sides of the body on alternate segments. In the Millepedes (Diplo- 



