DIPLOPODA THE FIRST RUDIMENT OF THE EMBRYO. 229 



general resemblance to the latter. This is also the case in the 

 Scolojiendridae, whereas, in the Scutigeridae and the Lithobiidae, 

 the embryos leave the egg with only seven pairs of legs (not taking 

 into account the maxillipedes). The number of legs is completed 

 during post-embryonic development. But since the young animals 

 in those cases also possess essentially the form of the mother, their 

 post-embryonic development, accomplished through several moults, 

 is fairly simple. The Chilopoda have been divided according to 

 this distinction in the manner of their development into Chilopoda 

 epimorpha (Scolopendridae, Geopliilidae) and Chilopoda anamorpha 

 (Scutigeridae, Lithobiidae). 



B. Diplopoda. 



The embryos of those Diplopoda whose ontogeny has as yet been 

 investigated (Polyxenus, Glomeris, Polydesmus, Strongylosoma, Julus), 

 leave the egg-envelope at a stage when only comparatively few 

 segments are developed and with only three well-developed pairs 

 of legs (Figs. 121 B, p. 235, and 122, p. 237). As contrasted with 

 the Chilopoda, which possess a large number of segments when 

 hatched, the young Diplopoda are thus comparatively far removed 

 from the adult form. They have been distinguished as larvae, but 

 it should be pointed out that, in those parts of the body that are 

 developed, they already show the organisation of the adult. 



The First Rudiment of the Embryo. 



Flexure of the Germ-band. 



Julus. The formation of the germ-band and the first rudiment of 

 the embryo seem to appear in the same way as in Geoj)lnlus, but the 

 germ-band does not in this case extend so far over the egg, and does 

 not, therefore, assume a marked dorsal flexure. "When the cephalic 

 lobes have appeared as rudiments, the stomodaeum lies between 

 them and the proctodaeum, almost at the posterior end of the 

 germ-band, and when, further, the post-cephalic segments have 

 become marked off and show the rudiments of limbs, a transverse 

 furrow appears between the sixth and seventh segments and soon 

 deepens. This is the same process as that which, in Geophilus, 

 results in the transition from the dorsal to the ventral curvature 

 (cf. Fig. 113). Since, however, the germ-band in Julus is small 

 as compared with the mass of the whole egg, the former sinks 

 into the yolk during this process (Fig. 116 A). The posterior and 

 still undifferentiated portion of the germ-band now lies bent parallel 



