CHAPTER XIV 
PHYLUM ARTHROPODA—(continued) 
Classes (continued)—ONYCHOPHORA or PROTOTRACHEATA ; 
Myriopopa; and INSECTA 
‘THESE three classes form a series of which winged insects 
are the climax. The type Levipatus is archaic, and links 
the series to the Annelids: the Myriopods lead on to the 
primitive wingless insects. All breathe by trachese—tubes 
which carry air to the organs of the body—and all have 
antenne ; hence they are often united under the title 
‘Tracheata Antennata. 
First Class of Tracheata Antennata.—ONYCHOPHORA or 
PROTOTRACHEATA 
GENERAL CHARACTERS 
The body ts worm-like in form, soft-skinned, and without 
external segmentation. 
The appendages are—a pair of prominent pre-oral antenna, 
a pair of jaws in the mouth, a pair of slime-secreting oral 
papilla, which development shows to be true appendages, 
numerous pairs of short, imperfectly jointed legs, each with 
two claws, and a pair of anal papille, which are rudt- 
mentary appendages. The legs contain peculiar (crural) 
glands. 
Respiration is effected by numerous unbranched trachee 
with openings irregularly scattered. The heart ts an elongated 
dorsal vessel with valvular ostia, There ts a series of 
nephridia in the legs. The halves of the ventral nerve-cord 
are widely separate. All are viviparous. 
