XI 



PHYLUM ARTHROPODA 



593 



nut 



lirfi 



imperfectly _cut off from the general body-cavity by a longitudinal 

 partition. 



The organs of respiration (Fig. 489) are delicate, unbranched 

 or rarely branched, tracked tubes, lined with a thin chitinous layer 

 exhibiting fine transverse striations. Groups of these open in 



little depressions of the integu- 

 ment, the tracheal pits (tr.p.), the 

 external openings of which are 

 known as the stigmata (tr.o.). 

 The stigmata are usually distri- 

 buted irregularly over the surface, 

 with a tendency to arrangement 

 in rows in P. capensis. By 

 means of these tubes air is con- 

 veyed to all parts of the body. 



A series of pairs of glands, the 

 coxal or crural glands (Fig. 488, 

 cox. gld.}, lie in the lateral com- 

 partments of the body-cavity, and 

 their ducts open on the lower 

 surfaces of the legs just outside 

 the nephridial apertures. They 

 are absent in the female except 



an 



FIG. 488. Dorsal view of the internal organs 

 oi Peripatus. an. anus; ant. antennae; 

 brn. brain ; cox. gld. coxal gland of the seven- 

 teenth leg ; $ gen. male genital aperture ; 

 ne. co. nerve-cord ; neph. nephridia ; or. 

 pap. oral papillae ; phar. pharynx ; sal. gld. 

 salivary gland ; si. gld. slime gland ; stom. 

 stomach. (Combined from Balfour.) 





--tr.o. 



FIG. 489. Section through a tracheal fpit 

 and diverging bundles of tracheal tubes 

 of Peripatus. tr. tracheae ; tr. c. cells 

 in walls of tracheae ; tr. o. tracheal stigma ; 

 tr. p. tracheal pit. (From Camb. Nat. Hist., 

 after Balfour.) 



in P. capensis, and their number and arrangement differ in the 

 males of the various species. Also opening on the ventral surfaces 

 of the legs are a series of thin-walled vesicles the coxal organs : 

 these occur in both sexes and are capable of eversion and retraction. 

 A pair of large glands the slime-glands (si. gld.} opening at 



