EXPERIMENTS ON ARTHROPODS 



103 



the respiratory nerves must originate in the abdomi- 

 nal ganglion-chain. The conditions existing in Verte- 



FIG. 31. LIMULUS POLYPHEMUS WITH THE CENTRAL NERVOUS 



SYSTEM EXPOSED. 



o, supracesophageal ganglion ; c, commissure ; , suboesophageal ganglion ; I-IV (V and 

 VI A 6d.), abdominal ganglia of the respiratory segments. 



brates evidently gave rise to the idea of a coordinating 

 ganglion located in the head. In Vertebrates the 



