3l8 THE INVERTEBRATA 



away from light and enemies. Yet it can hardly be doubted that the 

 Onychophora are a division of the Arthropoda which has preserved 

 more primitive features of an ancestral race than any other living 



Fig. 214. Peripatus capensis, x very slightly. From Sedgwick. 



forms, terrestrial or aquatic. Such features are in all probability the 

 thin cuticle, the muscular body wall, the annelid-like eye, the small 

 number of head segments, the complete series of segmental excretory 

 organs, the presence of cilia and possibly also the parapodia-hke 

 limbs. 



The thinness of the cuticle is responsible for the absence of external 

 segmentation (save for the repetition of the appendages). The head 

 (Fig. 215) bears three pairs of appendages which are none of them 



Fig. 215. Peripatus capensis, S- Ventral view of anterior end. ant. pre- 

 antenna; o.p. oral papilla; 7. jaw; i, first trunk appendage. After Sedgwick. 



very highly developed. While elsewhere in the arthropods the first 

 segment is present in the embryo but disappears in the adult, here it 

 persists and bears a pair of appendages which may be caW^dpreantennae 

 (to distinguish them from antennae). They are rather long and very 

 mobile, but not retractile like the tentacles of the slug. The next seg- 

 ment bears the jaws, which are not unlike enlarged claws of the trunk 

 appendages and so bite with the tip and not the side. They are more- 

 over tucked within the oral cavity. But they are borne on muscular 

 papillae arising in the embryo and must without doubt be regarded 

 as appendages. 



