No. I.] STUDIES ON LIMULUS. 97 



3. Sympathetic Systems. 



a. Late7-al Sympathetic. page 



Description by Milne-Edwards 166 



Location, extent, relations to branchio-thoracic muscles, and the seg- 

 mental cardiac and haemal nerves 166 



Description of lateral sympathetic nerve as found in one specimen 166 



Ganglionic enlargements mentioned by Milne-Edwards 169 



b. Nerves of Hea>-t. 



Milne-Edwards's description of the cardiac nerves 169 



(i) The Cardiac Plexus. 



Median ganglionated nerve 170 



Lateral cardiac nerves and plexus 170 



(2) Segmental Cardiac N'erves. 



General description 170 



Fused branches of seventh and eighth neuromeres, and their distribu- 

 tion ; anterior branches, pericardial nerve 171 



Post-cardiac nerves 172 



Cardiac branch from the sixth neuromere 172 



Relation of segmental cardiac nerves to ostia of heart 172 



C. Nerves of Alimetitary Tract. 

 (i) The Rostral Nerves. 



(2) Stomodaeal Nerves. 



Milne-Edwards's description of the ganglion upon the side of the pro- 

 ventriculus, and branches of the stomodaeal nerves going to the 

 intestine and to the heart 173 



(3) Intestinal Nerves. 



Innervation of posterior part of intestine, and the rectal ganglion of 



Milne-Edwards 174 



Typical arrangement of intestinal nerve in region of first three bran- 

 chial neuromeres 17 c 



Arrangement in posterior neuromeres 17^ 



Suggestions of elaborate plexus surrounding intestine 176 



Intestinal nerves of anterior neuromeres 176 



Summary. 



1. Sixteen neuromeres besides fore-brain 177 



2. Elementary part of each neuromere and exception to rule 177 



3. Neuromeres correspond to metameres 177 



Exceptions to this rule 178 



4. Brain divisible into four regions 178 



5. Peculiarities of accessory brain or " vagus region " 178 



6. The typical cranial and abdominal neuromeres 178 



7. Innervation of intestine 179 



8. Cardiac nerves 179 



