454 ZOOLOGY. 



the appendages with which their abdomen is provided. These 

 are the podurellse (Fig. 430), the lepisma, machilis 

 592), &c. 



CLASS OF THE MYKIAPODA. 



549. The myriapoda (many feet) respire air by means 

 of tracheae, like insects, but they differ considerably from these 

 animals, as well as from the arachnides (spiders), by their 

 general conformation. Not only they never have wings, but 

 their body, much elongated and divided into a great number 

 of rings, carries on each of these segments at least a pair of 

 limbs, besides the number of these organs, always twenty-four 

 at least, or more ; nor is there any line of demarcation between 

 the thorax and the abdomen. They somewhat resemble ser- 

 pents, or worms with feet ; but their internal organization 

 brings them nearer to ordinary insects, excepting that their 

 circulatory system is much less incomplete. 



Fig. 493. lulus ; Millipede. 



The head of the myriapoda is provided with two small 

 antennse, and with two eyes, generally farmed by the reunion 

 of ocelli. Their mouth is formed for mastication, and is pro- 

 vided with a pair of bi-articulated mandibles, followed by a 

 sort of lip with four divisions, and with two pairs of appen- 

 dages resembling little feet. The number of the rings of their 

 bodies varies, and sometimes these segments appear re-united, 

 two and two, in such a way that each moveable segment carries 

 two pairs of limbs (Fig. 493). These last organs terminate 

 only in a single hook. Finally, there exists on either side of 

 the body a series of stigmata, in communication with trachea?, 

 formed in the same way as those of ordinary insects. The 

 myriapoda experience metamorphoses in youth, but these 



