No. I.] 



STUDIES ON LIMULUS. 



I6l 



nerve very close to the ganglion and is either double at its 

 origin or divides, not far from its origin, into two branches. One 

 branch joins the plexus in the longitudinal muscles ; the other 

 goes to the intestine and in the majority of cases sends also a 

 branch to the haemo-neural muscle {Ji.n.my^) of its own meta- 



FiG. 17. — Diagram of the first gill, from the posterior side, showing the distribution of the gill 

 nerve to the gill book (about natural size). 



g.b., gill book ; i.l., inner lobe of the appendage ; m.l., median lobe of appendage ; 

 O.I., outer lobe of appendage. 



Nerves: ^.5.?^., external branchial nerve ; .^.«., gill nerve; i.i5.«., internal branchial 

 nerve; m.b.n., median branchial nerve; n.n.'^, neural nerve of the ninth neuromere. 



mere. In the last gill neuromere the double nature of the 

 intestinal branch was not found, but as these nerves are all 

 very delicate some of the branches might easily be overlooked 

 in dissection. Sometimes the branch which supplies the in- 

 testine goes some distance in the connective tissue, and divides 

 before entering the intestine ; and it has been seen to anastomose 

 with the intestinal branches from the other neuromeres. 



(b) The Cardiac Branches. — The cardiac branch in the 



