EXPLANATION OF PLATE VIII. 



FIG. 22. Palinurus sp. Dorsal view, heart displaced posteriorly. I-V, nerves to 

 corresponding ambulatory appendages ; yn, nerve to third maxilliped ; I, 2, nerves 

 to adductor muscles and heart ; 3-6, nerves ramifying in the arterial plexus on the 

 adductor muscles ; 7, 8, cardiac nerves. 



FIG. 23. Heart and heart-nerves of Limulus polyphemus. Dorsal view, a, 

 anterior artery ; la, lateral arteries ; lit, lateral nerves ; mnc, median nerve-cord ; 

 os, ostia. 



FIG. 24. Heart of Limulus. Dorsal view. Showing the connection of the ven- 

 tral with the cardiac nervous system, nine, dorso-median nerve-cord on the heart ; 

 pn, pericardial nerves ; 7, 8, branches from the two posterior haemal nerves from 

 the brain ; 9-13, branches from the haemal nerves of the abdominal ganglia. 



FIG. 25. Brain and abdominal ganglia of Limulus. Dorsal view. I-V, nerves 

 to corresponding ambulatory appendages ; 2-8, haemal nerves from the brain. The 

 herves 7 and 8 carry the inhibitory fibers to the heart. 9-13, haemal nerves from the 

 thoracic ganglia, carrying accelerator fibers to the heart. 



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