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FIRST BOOK OF ZOOLOGY. 



ally equaling, and eometimes exceeding, the width of the 

 body. 



The segments in inanj cases are unequal in length, some 

 of them being very short and alternating with long ones, 

 though all bear a pair of legs below. The antennae are much 

 longer than the legs, and are often composed of a great many 

 joints. A pair of modified legs reach out behind and look 

 like a hinder pair of antennae. 



In a few forms the eyes are compound as in the insects, 

 while in others the eyes are separate as in the spider, and 

 are called ocelli. These are grouped on each side of the head, 

 at the base of the antennae. 



A magnified view of the head, showing group of 

 Fig. Ilfi-COMMON Cektiied.". eyes at the base of antennae. A few joints only of 



Natural Size. the antennae are shown. 



115. The jaws or mandibles are large and jointed, with 

 the terminal joint long and shai^ as in the spiders. The 

 other pairs of jointed appendages act also as mouth-parts. 

 The under lip is notched with fine teeth, as shown in the fol- 

 lowing figure, which repres3nts the under surface of the head 

 of the species of centipede shown in Fig. 116. 



