92 



WHEELER. 



[Vol. VIII. 



These fusions become more intimate as the time for hatching 

 approaches, so that the ventral cord finally consists of only- 

 ten ganglia instead of sixteen, the original number. 



-VX?,^C* 



i(>.cvos;i 



\\-\^. 



Fig. VII. 

 A-D. Diagrams of four consecutive stages in the development of the brain 

 and nerve-chain of the Xiphidium embryo. I, cephalic ; II, thoracic ; III, 

 abdominal region ; jA, stomodseum ; ««., anus ; e, optic plate ; pc^{o.g), first 

 protocerebral lobe, or optic ganglion ; pc^, pc^, second and third protocerebral 

 lobes ; dc, deutocerebrum ; tc, tritocerebrum ; 1-16, the sixteen postoral ganglia ; 

 po.c, postoral commissure ; fp., furcal pit ; ac, anterior ; pc, posterior ganglionic 

 commissure ; ag., anterior ; pg., posterior ; eg., central ; Ig., lateral gangliomeres. 



The description of the ventral nerve-cord of Xiphidium here 

 given applies equally well to the other Orthoptera which I have 

 studied {Blatta germanica, Melanoplus fcviur-rubriiui) . The 



