CHILOPODA DEVELOPMENT OF THE EXTERNAL FORM. 



225 



here, perhaps, as there, the character of post-oral limbs. The difference in the 

 position of the antennae in the two embryos may, perhaps, be explained by 

 imagining a change both of the time and the place of their appearance, such as 

 is occasionally found in other embryonic rudiments. 



In the embryo of Geophilus depicted in Fig. Ill, behind the oral aperture, 

 two somewhat large prominences {ul) can be seen, resembling a pair of limbs, 



R. 





Fig. 112. — Two embryos of Geophilus, lateral aspect. The germ-band surrounds a large part 

 of the yolk and still shows the dorsal curvature. The two lateral swellings found in the 

 embryo at the stage depicted in Bare omitted for the sake of clearness (after Metschnikoff). 

 a, anus ; at, antenna ; d, yolk ; Jcl, cephalic lobe ; md, mandible ; mx lt mx„, first and second 

 maxillae ; rap, maxillipedes ; m\v, mouth-parts ; p (p,, p„), legs ; si, caudal lobe. 



but lying in front of the mandibles. Sograff calls these structures the lower 

 lip, but it is not clear whether he actually considers them to be limbs, and to 

 what part of the adult he refers them. The mouth-parts known to us in the 

 Chilopoda only develop behind these, as already seen (Figs. 109-111). Similar 

 structures met with in the Insecta are not regarded as limbs, but as a lower 

 lip. 



