328 



MANUAL OF ZOOLOGY. 



coalescent, and have their appendages specially modified to 

 subserve prehension " (Huxley). Pauropus has only nine pairs 

 of legs ; but, with this exception, eleven pairs of legs is the 

 smallest number known in the order. 



The respiratory organs, with one exception (i.e., Pauropits), 



Fig. 169. A, Lithobius forficatns, enlarged and viewed from above: an Antennae; 



f Foot-jaws; h Head. B, Head of Lithobius Leachii, viewed from below (after 



Newport) : an Antennae ; f Hooked foot-jaws ; / Lower lip, composed of two pieces. 



C, Head of Lithobiits forficatus, viewed from above (after Gervais) : an Antenna ; 



e Eye. 



agree with those of the Insecta and of many of the Arachnida 

 in being " tracheae " that is to say, tubes, which open upon 

 the surface of the body by minute apertures, or " stigmata," 

 and the walls of which are strengthened by a spirally-coiled 

 filament of chitine. The tracheae may or may not anastomose 

 with one another as they do in Insects. 



The somites, with the exception of the head and the last 

 abdominal segment, are usually undistinguishable from one 

 another, and each generally bears a single pair of limbs. In 

 some cases, however, each segment appears to be provided 



