No. I.] STUDIES ON LIMULUS. 1 69 



separate entirely from the haemal nerve before the recurrent 

 branch is given off. 



In the eleventh and twelfth neuromeres the recurrent branches 

 are given off from the haemal nerves {Ji.n."^^^'^) before the 

 cardiac branches {s.c.n."^^^'^) separate from them. 



A portion of the cardiac branch {s.c.n."f) of the fourteenth 

 neuromere separates from the haemal nerve (Ji.n/'*) near the 

 ventral cord and, opposite the lateral sympathetic, receives 

 another fiber which separates from the haemal nerve close to 

 the origin of the recurrent sympathetic branch. 



The last recurrent sympathetic branch arises from the four- 

 teenth haemal, or first post-branchial nerve {Ji.n."i). The post- 

 cardiac {s.c.n.''f) separates from the haemal nerve some distance 

 beyond the origin of the sympathetic branch. 



Under favorable conditions small recurrent fibers may be seen 

 in the angles between the roots of the sympathetic branches 

 and the outer, or integumentary portions of the haemal nerves. 



The ganglionic enlargements referred to by Milne-Edwards 

 could not be found. He probably referred to the flattened por- 

 tions which sometimes occur at the junctions of the lateral 

 sympathetic with the haemal nerves. These flattenings are 

 likely to occur wherever a nerve passes between two muscles 

 or other parts in close contact with each other ; they do not 

 contain any ganglion cells. 



b. Ne}"ves of the Heart. 



The only mention we have of the cardiac nerves of Limulus 

 is found in " Anatomic des Limulus," by Milne-Edwards. " Sur 

 les c6tes de I'estomac se trouvent aussi deux filets d61icats et 

 tenus qui se rendent a un nerf volumineux situe sur la ligne 

 mediane du coeur et dans toute la longueur de cet organ. Ce 

 nerf cardiaque, qui s'amincit beaucoup vers les extremit^s du 

 vaisseau dorsal, est au contraire tres-large vers la partie moyenne 

 de celui-ci ; effectivement, il presente un certain nombre de ren- 

 flements situ^s au niveau de chaque paire d'ouvertures vascu- 

 laires, et de ces points partent des filets qui se dirigent a droite 

 et a gauche sur les parois adjacentes." 



