The haemal nerves of the accessory brain pass through the occipital ring to the sides of the body between the operculum and the sixth cephalothoracic appendage. The seventh innervates the posterior angles of the cephalothorax, the eighth the opercular portion of the abdomen. The next five haemal nerves arise from the five branchial neuromeres, pass out anterior to the gills to the sides of the abdominal carapace, and innervate the first five spines upon the sides of the abdomen. The first post-branchial nerve innervates the last abdominal spine; the second post-branchial nerve and one branch of the third post-branchial innervate the posterior angles of the abdomen and the muscles of the telson; and the caudal branch of the third post-branchial nerve innervates the telson. Intestinal branches arise from all the haemal nerves from the sixth to the sixteenth, and pass to the longitudinal abdominal muscles and to the intestine. Cardiac nerves arise from all the haemal nerves from the sixth to the thirteenth. Six of the cardiac nerves communicate with the lateral sympathetic nerve (24), which innervates the branchio-thoracic muscles (16). Two post-cardiac nerves arise from the first two post-branchial nerves, and passing to the haemal side anastomose with a branch from the last cardiac nerve, and innervate the extensors (27) of the telson and the epidermis behind the heart. 1, Cephalothorax; 2, median eye-nerve; 3, proventriculus; 4, tergo-proplastral muscles; 5, haemal branch of integumentary nerve; 6, entocoxites; 7, 2nd haemal nerve; 8, right olfactory nerve; 9, median olfactory nerve; 10, intestine; 11, endosternite; 12, fore-brain; 13, origin of 4th neural nerve; 14, lateral nerve; 15, lateral eye; 16, branchio-thoracic muscles; 17, external branchial muscles; 18, tendinous stigmata; 19, branchial cartilages; 20, intestine; 21, abdominal endochondrites; 22, ventral cord; 23, haemo-neural muscles; 24, lateral sympathetic nerve; 25, occludor ani; 26, sphincter ani; 27, extensors of telson; 28, anus; 29, flexors of telson; 30, lateral projections of abdomen; 31, nerves of spines; 32, external branchial muscles. ] [Illustration: FIG. 157.—The markings on the sand made by the female _Limulus_ when depositing eggs. Towards the lower end the round “nests” cease to be apparent, the king-crab being apparently exhausted. (From Kishinouye.) About natural size. ]