192 PATTEN AND REDENBAUGH. 



following nine haemal nerves (/;.«.*"'*) are cut off beyond the cardiac branches. 

 The second post-branchial nerve {Ji.n}^) is cut off beyond its branch to the telson 

 muscles. Both branches of the haemal nerve (/4.«."') are represented extending 

 into the telson (tel^. 



The intestinal nerves (/'.w.''''^) are shown arising from the haemal nerves and 

 entering the intestine. Those from the sixth and seventh neuromeres (i.n.^ ^"<^ 7) 

 pass through foramina in the endocranium and communicate with a plexus in the 

 longitudinal abdominal muscles before entering the intestine. The eighth passes 

 just posterior to the endocranium and joins the same plexus. Those from the 

 first four branchial neuromeres (z.w.'"'^) arise very near the abdominal ganglia and 

 are double in their origins, the anterior branches joining the above-mentioned 

 plexus, and the posterior branches entering the intestine. The thirteenth, four- 

 teenth, and fifteenth are somewhat complicated in their relations and will be 

 described to better advantage under Fig. 4. The fifteenth extends far back 

 towards the rectum and anastomoses with the sixteenth (/.«.'*), which arises from 

 the caudal branch of the sixteenth haemal nerve (h.n}^) and innervates the 

 rectum and anal muscles. 



The segmental cardiac nerves (j.c.w.^"") arise from the haemal nerves of the 

 sixth to the thirteenth neuromeres respectively. The most anterior one (s.c.n.^^ 

 passes haemally to the inter-tergal muscles and epidermis in median line, haemal 

 to the heart, but the connections vrith the cardiac plexus have not been made out. 

 The next two {s.c.nJ ^^^ ^) fuse to form a large nerve, which likewise passes 

 haemal to the heart, to the inter-tergal muscles, and epidermis, but has not been 

 observed to connect directly with the cardiac plexus. It, however, sends poste- 

 riorly a branch, the pericardial nerve (/■«.), which in turn gives a branch to each 

 of the cardiac nerves of the branchial neuromeres (j.c.w. '"''), and then continues 

 onward to the posterior margin of the abdomen. This nerve lies in the epidermis 

 haemal to the heart. The median and lateral cardiac nerves (tn.c.n. and l.c.n.) are 

 seen upon the walls of the heart. The five cardiac nerves (j.^. «.'"") from the 

 branchial neuromeres pass haemal to the heart, in the epidermis, to the median line, 

 and dip down to the median nerve {m.c.n.) of the heart opposite the last five pairs 

 of ostia {o.s.^'^^). They communicate with the pericardial nerve {p-n.) and also 

 with the lateral sympathetic nerve {l.s.n.). 



Two post-cardiac nerves (s.c.nM ^"""^ '5) pass from the first and second post- 

 branchial nerves {h.n.^'^ ^^"^ 'S) to the epidermis posterior to the heart. 



The last cardiac nerve {s.c.n}^) and the two post-cardiac nerves i^s.cn.^* ^^^ 'S) 

 give off branches which anastomose with each other and innervate the extensors 

 of the telson. 



The lateral sympathetic nerve {l.s.n.) receives branches from all the neuromeres 

 from the eighth to the fourteenth, either through the cardiac nerves or the haemal 

 nerves, and innervates the branchio-thoracic muscles, extending with these far 

 into the cephalothorax. 



Fig. 4. This drawing is intended to show the intestinal nerves from the 

 haemal side, and is made to the same scale as Fig. 3. Most of the heart and a 

 large portion of the intestine have been removed, leaving exposed the haemal 

 sides of the endocranium, ventral cord, muscles inserted on the endocranium, and 

 the plexus of intestinal nerves. 



The anterior end of the heart {ht.) with the aortic arches (ao.a.) and frontal 



