172 PATTEN AND REDENBAUGH. [Vol. XVI. 



pericardial nerve is lost in a plexus of nerves, some of the 

 branches of which extend in the epidermis to the posterior 

 margin of the abdomen. 



The cardiac nerve {s.c.nP) of the last branchial neuromere 

 differs from the others in that it gives a branch to a slip of the 

 extensor muscle of the telson, which is inserted upon the last 

 three entapophyses. Similar branches from the first two post- 

 cardiac nerves go to the same muscle, anastomose with this nerve 

 and with each other, and send a branch in the epidermis to the 

 posterior end of the abdomen. 



The two post-cardiac nerves {s.c.n."^^^^'^) also send branches 

 to the epidermis near the median line. As the heart does not 

 extend back of the thirteenth metamere, the post-cardiac nerves 

 have no connection with this organ. 



In the sixth thoracic neuromere a large cardiac branch {s.cm.^) 

 is given off from the sixth haemal nerve {Ji.nP). This does not 

 communicate with the lateral sympathetic, but passes haemally 

 and anteriorly outside of the branchio-thoracic muscles, and 

 enters the large inter-tergal muscles haemal to the heart. Here 

 its branches anastomose with those of the fused seventh and 

 eighth cardiac nerves {s.c.ny^'^^^). Some of the finer branches 

 innervate the epidermis also, and possibly communicate with 

 the median nerve of the heart, although this connection has 

 not been observed. 



A small nerve, which could not be traced out, was found 

 arising from the fifth haemal nerve {h.n.^) at a point cor- 

 responding to the origins of the cardiac nerves of other 

 neuromeres. 



It is a curious fact that, leaving out the post-cardiac nerves, 

 there are as many segmental cardiac nerves as there are ostia 

 in the heart. The cardiac nerves {s.c.n.^^^) from the five bran- 

 chial neuromeres enter the heart opposite the five posterior 

 pairs of ostia {os.'>~'^). This leaves three segmental cardiac 

 nerves {s.c.n.^~^) corresponding to the three anterior pairs of 

 ostia (os.^^). If these have any connections with the median 

 nerve of the heart, the connection will probably be found oppo- 

 site the three anterior pairs of ostia, inasmuch as the connec- 

 tions of the other five cardiac nerves with the median cardiac 



