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TEXT-BOOK OF ENTOMOLOGY 



which are intermediate between the malipedes and the feet; Meinert 

 does not allow that these are mouth-appendages. 



The embryology of Geophilus by Metschnikoff shows plainly the 

 four pairs of post-antennal appendages. The embryo Geophilus is 

 hatched in the form of the adult, having, unlike the diplopods, no 

 metamorphosis, its embryological history being condensed or abbre- 

 viated. But in examining Metschnikoff' s figures certain primitive 

 diplopod features are revealed. The body of the embryo shortly 

 before hatching is cylindrical; the sternal region is much narrower 

 than in the adult, hence the insertions of the feet are nearer together, 

 while the first six pairs of appendages begin to grow out before the 



FIG. 12. Structure of a chilopod. A, Lithobiu* americanus, natural size. , under side of 

 head and first two body-segments and legs, enlarged : ant, antenna ; 1, jaws ; 2, first accessory jaw ; 

 c, lingua; 3, second accessory jaw and palpus; 4, poison-jaw. (Kingsley del.) C, side view of 

 head (after Newport) : ep, epicranlmn ; /, frontal plate ; sc, scute ; 1, first leg ; up, spiracle. 



hinder ones. Thus the first six pairs of appendages of the embryo 

 Geophilus correspond to the antennae, two pairs of jaws, and three 

 pairs of legs of the larval Julus. These features appear to indicate 

 that the chilopods may be an offshoot from the diplopod stem. The 

 acquisition of a second pair of legs to a segment in diplopods, as in 

 the phyllopod Crustacea, is clearly enough a secondary character, 

 as shown by the figures of Newport in his memoir on the develop- 

 ment of the Myriopoda (PI. IV.). Thus the tendency in the 

 Myriopoda, both diplopods and chilopods, is towards the multipli- 

 cation of segments and the elongation of the body, while in insects 

 the polypodous embryo has the three terminal segments of the 



