CHAPTER XIV 



PHYLUM ARTHROFOD A— {continued) 



Classes {continued)— Onyckofhora or Prototracheata ; 

 Myriopoda ; and Insecta 



These three classes form a series of which winged insects 

 are the cUmax. The type Peripatus is archaic, and hnks 

 the series to the AnneUds : the Myriopods lead on to the 

 primitive wingless insects. All breathe by tracheae — tubes 

 which carry air to the organs of the body — and all have 

 antennae ; hence they are often united under the title 

 Tracheata Antennata. 



First Class of Tracheata Antennata.— On ychophora or 



Prototracheata 



General Characters 



The body is worm-like in form, soft-skinned, and without 

 external segmentation. 



The appendages are — a pair of prominent pre-oral antennae, 

 a pair of jaws in the mouth, a pair of slime-secreting oral 

 papillce, which development shows to be true appendages, 

 numerous pairs of short, imperfectly jointed legs, each with 

 two claws, and a pair of anal pqpillce, which are rudi- 

 mentary appendages. The legs contain peculiar {crural) 



glands. 



Respiration is effected by numerous unbranched tracheee 

 with openings irregularly scattered. The heart is an elongated 

 dorsal vessel with valvular ostia. There is a series of 

 nephridia in the legs. The halves of the ventral nerve-cord 

 are widely separate. All are viviparous. 



In its possession of tracheee and nephridia this type is an 



interesting connecting link ; in many ways it seems to be an 



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