CHAPTER XLIV 



ONYCHOPHORA AND MYRIAPODA 



Onychophora (onikSf ora; G., onychos, claw, and phoros, bearing) 

 is a class of the phylum Arthropoda which in a natural classification 

 should come first, since it is not only the simplest of the arthropods but 

 has a pronounced resemblance to the annelids, suggesting a derivation of 

 arthropods from annelid-like ancestors. 



307. Onychophora. — The typical genus of this class is Peripatus, 

 which contains numerous species reported from widely separated local- 

 ities in Australia, New Zealand, Tasmania, New Britain, the Malay 

 Archipelago, South America, Mexico, West Indies, and Africa. It is a 

 wormlike form with a soft skin covered by papillae, each papilla bearing 



Fig. 176. — Peripatus; an individual shown entangling a cockroach in sticky threads 

 formed by a secretion ejected from papillae on its head. {From Pearse, "General Zoology," 

 by the courtesy of Henry Holt & ComjMny.) 



a spine. Metamerism is not marked externally, but there is a series of 

 short, fleshy legs in pairs, each ending in two claws. There is also an 

 oral papilla on each side of the mouth and a pair of simple eyes. 



Peripatus shows a number of annelid-like characteristics. The skin 

 is thin and not so heavily chitinized as in the arthropods generally, there 

 are paired and segmentally arranged nephridia in all but the first two 

 metameres, and there is a marked resemblance to the annelids in the general 

 arrangement of internal organs. In other ways, however, it seems to be 

 truly an arthropod, since it has tracheae (Sec. 313), appendages modified 

 to form jaws, and body cavities which are hemocoelic. It differs, how- 

 ever, both from other arthropods and from annelids in having a single 

 pair of jaws, in the texture of the skin, and in the simplicity of the 

 metamerism. 



The species of Onychophora live in crevices in rocks, under stones, 

 and in the dark recesses of rotting logs, where they move slowly about 

 from place to place, always avoiding the light. When disturbed a very 



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