ANATOMY HABITS 267 



oif just beyond the point wliere it fuses with the second haemal nerve (8). The 

 stoinodaeal nerve (6) ramifies over the oesophagus and proventriculus. 



The second haemal nerve (8) passes to the anterior extremity of the carapace ; 

 its haemal branch is cut off opposite the proventriculus. An intestinal branch 

 arises from near its base and disappears behind the anterior cornu of the endo- 

 sternite. 



The next three haemal nerves (36) are cut off close to the brain, and the 

 following nine haemal nerves are cut off beyond the cardiac branches. The fifteenth 

 haemal nerve (29) is cut off beyond its branch to the telson muscles. Both 

 branches of the haemal nerve are represented extending into tlie telson (25). 



The intesti.nal nerves are shown arising from the haemal nerves and entering the 

 intestine. Those from the sixth and seventh neiiromeres pass through foramina in 

 the endosternite, and communicate with a plexus in the longitudinal alidominal 

 muscles before entering the intestine. The eighth passes just posterior to the endo- 

 sternite and j'oins the same plexus. Tliose from the first four branchial neuromeres 

 arise very near the alidominal ganglia, and are double in their origins, the anterior 

 branches joining the above-mentioned plexus, and the posterior branches entering 

 the intestine. The fifteenth extends far back towards the rectum and anastomoses 

 with the sixteenth, which arises from the caudal branch of the sixteenth haemal 

 nerve, and innervates the rectum and anal muscles. 



The segmental cardiac nerves (18) arise from the haemal nerves of the sixth to 

 the thirteenth neuromeres respectively. The most anterior one passes to the inter- 

 tergal muscles and the epidermis in the median line, but the connections with the 

 cardiac plexus luive not been made out. The next two (18) fuse to form a large 

 nerve, which passes to the iuter-tergal muscles and epidermis, but has not been 

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

 a branch, the pericarilial nerve (20), which in turn gives a branch to each of the 

 cardiac nerves of the branchial neuromeres, and then continues onward to the 

 posterior margin of the abdomen. This nerve lies in the epidermis. The median 

 and lateral cardiac nerves (22 and 21) are seen upon the walls of the heart. The 

 five cardiac nerves from tlie branchial neuromeres pass, in the epidermis, to the 

 median line, and dip down to the median nerve (22) of the heart opposite the last 

 five pairs of ostia (17). They communicate with the pericardial nerve (20) and also 

 with the lateral sympathetic nerve (30). 



Two post-cardiac nerves pass from the first and second post-branchial nerves to 

 the epidermis posterior to the heart. 



The last cardiac nerve and the two post-cardiac nerves give off branches which 

 anastomose with each other and innervate the extensors of the telson. 



The lateral sympathetic nerve (30) receives branches from all the neuromeres 

 from the eiglith 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. 



1, Mouth ; 2, rostral nerve in labruni ; 3, anterior commissure ; 4, chelicera ; 5, 

 olfactory nerves ; 6, stomodaeal nerve ; 7, lateral eye-nerve ; 8, 2nd haemal nerve ; 

 9, latei'al nerve; 10, median eye-nerve; 11, median eye ; 12, proventriculus; 13, 

 frontal artery ; 14, aortic arch ; 15, anterior liepatic duct of liver ; 16, heart ; 17, 2nd 

 ostium ; 18, 7th and 8th segmental cardiac nerves ; 19, one of the lateral arteries ; 

 20, pericardial nerve ; 21, lateral cardiac nerve ; 22, median cardiac nerve ; 23, 

 intestine ; 24, levator ani muscle ; 25, telson ; 26, anus ; 27, sphincter ani muscle ; 

 28, last Ijranchial appendage ; 29, 15th haemal nerve; 30, lateral sympathetic nerve; 

 31, 8th abdominal endochondrite ; 32, genital operculum; 33, chilarium ; 34, 

 endosternite ; 35, ventral nerve cord ; 36, 6th haemal nerve ; 37, origin of 6th 

 neural nerve. 



Limulus feeds partly on bivalves, but mainly on worms, especi- 

 ally Nereids, which it catches with its chelate limbs as it burrows 

 through the sand. The food is held immediately under the mouth 

 by the chelicerae, aided at times ])y the succeeding appendages ; 

 it is thus brought within range of the gnathobases of the 



