326 



PHYSIOLOGY OF THE INVERTEBRATA. 



thick commissures with the sub-cesophageal ganglion, which 

 corresponds to several pairs of ganglia fused together. This 





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sub-oesophageal ganglion leads into a ventral ganglionated 

 chain, which has three pairs of coalesced ganglia in the 

 thorax, and six pairs of closely connected and smaller ganglia 



