cxiv Introduction. 



Class, Myriopoda. 

 Air-breathing- Arthropoda in whicli the segments and their ap- 

 pendages make a nearer approach to homonomy than in either 

 Insecta or Arachnida, and in which the post-cephalic locomotor 

 appendages^ even when least numerous^ and amoimting to nine 

 pairs only as in Pimropii,s, are still more numerous than the similar 

 organs in either of the two other classes mentioned, except in the 

 larvae of certain Hymenoptera, Cimbex and TentJiredo, which possess 

 eight and seven pairs, respectively, of prolegs, besides the three pairs 

 of true legs. In the homonomy and number of their segments 

 and appendages, the Myriopoda resemble certain of the Crustacea, 

 with which Class they have often been ranked, as also in having the 

 first, or the first two pairs of post-cephalic appendages, subordinated 

 more or less completely to the manducatory organs, so as in one 

 order, Cldlopoda, to form ' foot-jaws,' and in another, Chilognatha, 

 to form 'labia' by the partial fusion and other modifications of 

 their coxae, whilst in Panropus the anterior pair of legs is rudi- 

 mentary. There is however no fusion of segments in the Myrio- 

 poda of the kind which produces a cephalo-thorax in Crustacea. 

 It may be added here that an additional point of similarity to the 

 Crustacea is manifested by the Myriopoda in their mode of growth ; 

 as their larvae instead of leaving the e^g, as insect larvae do, with 

 at least as many segments and legs as they ever afterwards possess, 

 leave the egg with a much smaller number of segments and legs 

 than by the periodical addition of segments at successive moultings, 

 they attain in the adult state. The Myriopoda however must be 

 classed with the air-breathing Arthropoda, not only on account of 

 their respiration being tracheal, except in the case of the diminutive 

 Fauropns, but also on account of the singleness of their antennae ; 

 the sessile position of their eyes ; their non-palpigerous mandibles ; 

 the fusion of their maxillae into a labium ; the large development 

 of their salivary and renal, and the rudimentary condition of their 



hepatic glands. 



The Myriopoda appear to stand midway between the two other 

 classes of air-breathing Arthropoda, as to the mutually correlated 

 and mutual supplementing complexity and simplicity of the circu- 

 latory and respiratory apparatus. Their digestive and nervous - 

 systems are closely similar to those of the larvae of Insects. 



