290 IULUS, POLYDESMTJS, GLOMERIS. 



the portions of decaying vegetable matter, on which they usually 

 feed. These animals are very harmless to Man. not being pos- 

 sessed of any poisonous organs ; aid they may be regarded as 

 positively benefiting him by the removal of substances whose 

 decay would otherwise be noxious. The common lulus of thig 

 country seldom much exceeds an inch in length ; but there is a 

 South American species, lulus maximus, which attains the 

 length of seven inches. The Polydesmus (Fig. 507) corresponds 

 with the lulidas in general structure and habits, but has the 

 body remarkably flattened. The Glomeris bears a strong resem- 

 blance to the Woodlice ( 799), in its oval form, and its habit 

 of rolling itself into a ball ; it is also remarkable from 

 its small number of segments, those of the body being 

 only twelve, as in Insects. The under surface of 

 the body, which is concave, has a row of small scales 

 on each side, which has been compared to the lateral 

 lobes of the Trilobites and some of the Isopod Crus- 

 tacea. Altogether the resemblance of this animal to 

 GIX>MERIS that group is very striking ; the chief difference being 

 in the nature of the respiratory organs. The animals 

 of this Order are remarkable for their power of emitting a dis- 

 agreeable odour, when they are alarmed. This seems to result 

 from a peculiar secretion, poured out from the stigmata or respi- 

 ratory orifices ; and it may be regarded as a means of defence, 

 which replaces the poison apparatus of the Centipedes. 



