1 6 PERIPATUS CHAP. 



The Body Cavity. 



The body cavity is formed of four compartments one central, 

 two lateral, and a pericardial (Fig. 14, D). The former is by far 

 the largest, and contains the alimentary tract, the generative 

 organs, and the slime glands. It is lined by a delicate endo- 

 thelial layer, and is not divided into compartments nor traversed 

 by muscular fibres. The lateral divisions are much smaller than 

 the central, and are shut off* from it by the inner transverse band 

 of muscles. They are almost entirely filled with the nerve-cord 

 and salivary gland in front and with the nerve-cord alone behind, 

 and their lumen is broken up by muscular bands. They further 

 contain the nephridia. They are prolonged into the feet, as is the 

 embryonic body cavity of most Arthropoda. The pericardium con- 

 tains a peculiar cellular tissue, probably, as suggested by Moseley, 

 equivalent to the fat-bodies of insects. 



Nephridia. 



In Peripatus capensis nephridia are present in all the legs. 

 In all of them (except the first three) the following parts may 

 be recognised (Fig. 11) : 



(1) A vesicular portion opening to the exterior on the ventral 



surface of the legs by a narrow passage. 



(2) A coiled portion, which is again subdivided into several 



sections. 



(3) A section with closely packed nuclei ending by a some- 



what enlarged opening. 



(4) The terminal portion, which consists of a thin-walled 



vesicle. 



The last twelve pairs of these organs are all constructed in a 

 very similar manner, while the two pairs situated in the fourth 

 and fifth pairs of legs are considerably larger than those behind, 

 and are in some respects very differently constituted. 



It will be convenient to commence with one of the hinder 

 nephridia. Such a nephridium from the ninth pair of legs is 

 represented in Fig. 11. The external opening is placed at the 

 outer end of a transverse groove at the base of one of the legs, 

 while the main portion of the organ lies in the body cavity in 

 the base of the leg, and extends into the trunk to about the level 



