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upward and backward around the oesophageal canal to the ventral end of the 

 cerebral ganglion. The latter arises from the back end of the ganglion together 

 with the former and turns forward and upward around the oesophagus and ends 

 in the supra-buccal ganglion. Several small nerves arise from the edges of the 

 upper surface of the ganglion. The fibres of these nerves radiate backward , 

 upward and forwaixl , and innervate the muscles between the skull and the base 

 of the arms. Five pairs of nerves or connectives come from the edge of the 

 ventral surface of the ganglion and diverge from one another as thej^ pass 

 forward around the pharynx from which thej' are separated by the buccal sinuses. 

 These ten nerves enter ten bi-aehial ganglia which lie in the corresponding arms, 

 and which are more properly called nerve-cords. Each ganglion or cord extends 

 from the base to the apex of the arm and tapers regularly from its large base 

 to a minute point. The bases of the ganglia are connected by slender nerve 

 tracts which with the ganglia form at the bases of the arms a nerve-ring, the 

 brachial ring. It is not certain , but probable , that the ganglia of the fourth pair 

 of arms are connected with this ring. 



The buccal nerve ring is formed by the suprabuccal and infrabuccal ganglia, 

 and encircles the oesophagus just back of the pharynx. The suprabuccal gang- 

 lion is attached to the inner surface of the septum that separates the two 

 buccal sinuses. Its dorsal surface receives two pairs of connectives , the cerebro- 

 buccal and the propedo-buccal , from the cerebral and propedal ganglia respectively. 

 From the ventral end of the ganglion arise four or five pairs of nerves which 

 pass to the muscles of the pharynx . and from the sides arise two connectives 

 which pass downward around the oesophagus to the infrabuccal ganglion. 



The infrabuccal ganglion is attached to the dorsal surface of the pharynx 

 betw'een the lateral salivary glands. Two pairs of nerves from this ganglion inner- 

 vate the odontophore and a pair of connectives arises from its dorsal end and 

 passes backward along the entire length of the oesophagus. These connectives , 

 the bucco-splanchnic , enter the splanchnic, "gastric", or "abdominal" ganglion 

 which lies on the upper surface of the dorsal end of the intestine between 

 the oesophagus and the caecum. 



The splanchnic ganglion gives off five large and two or more small nerves. 

 The largest nerve passes to the left between the caecum and the pancreas and, 

 entering the ridge from which the caecal folds arise , supplies them. Two large 

 nerves arise from the dorsal end of the ganglion and go between the stomach 

 and caecum , supplying the inner sides of both organs. One large and two small 

 nerves from the right side of the ganglion pass under the oesophagus to the 

 upper (anterior) caecal lobe. From the ventral end of the ganglion arise the 



