x PHYLUM ARTHROPODA 237 



Each jaw is composed of two curved, falciform, chitinous plates ; they 

 lie at the sides of the mouth enclosed by a circular lip. The jaws, as 

 well as the oral papillse, are developed as modified limbs. The legs are 

 not jointed ; each consists of a proximal part and a small distal part or 

 foot terminating in a pair of horny claws. 



In the internal anatomy (Fig. 130) the most important features are the 

 presence (i) of organs of respiration in the form of trachea unbranched 



FIG. 1 2Q. Ventral view of head of Peripatus capensis, with antennae, jaws, oral 

 papillae, and first pair of legs. (After Balfour.) 



or rarely branched tubes, groups of which open on little depressions of 

 the integument ; the external openings or stigmata are in some 

 species distributed irregularly over the. surface, in others arranged in 

 longitudinal rows: (2) of a series of pairs of nephridia (neph, ) similar 

 to those of the Annulata : and (3) of a nervous system consisting of 

 a brain (brn.), situated in the head, and two separate nerve cords (ne. co.) 



