142 PATTEN AND REDENBAUGH. [Vol. XVI. 



that surround it. It divides near the ganglion into the ento- 

 coxal {e.n), mandibular {m.n.), and pedal branches. The ento- 

 coxal branches, three in number, supply the muscles inserted 

 upon the entocoxite, and numerous sense organs in the ento- 

 coxite itself ; the mandibular branch supplies the mandibles ; 

 and the pedal branches the remainder of the appendage. In 

 the coxopodite the main pedal branch divides into an external 

 {e.p.n.) and an internal portion {i.p.n.). 



The thoracic haemal nerve, like the abdominal one, has an 

 intestinal, a cardiac, and an integumentary branch. The intes- 

 tinal branch {i.n.) arises at some distance from the brain ; 

 the cardiac branch (s.c.n.) does not communicate with the 

 lateral sympathetic, and its communication with the heart is 

 doubtful ; the integumentary nerve divides into a haemal and 

 a neural portion (/t. and n.). 



b. Nerves from the Mid-Brain (Text-fig. lo). 



The mid-brain region contains in addition to the nerves and 

 neuromere of the cheliceral segment a pair of stomodaeal nerves 

 and ganglia and three rostral nerves, arising from the pre-stomo- 

 daeal commissure. 



( I ) The Neural Nerves. — The neural nerves (Text-fig. i o ; 

 Pis. VI-VIII and X, Figs. 1-3, 11, and 12, 7i.n.') arise from 

 ganglionic swellings situated just back of the cerebral lobes, 

 and pass directly to the inside of the chelicerae. 



At the base of the neural nerve arises one or more external 

 pedal nerves {e.p.n.). They innervate the tergo-coxal muscles 

 (e.^, f.', l.m.^), and then pass into the chelicera outside of the 

 main nerve (i.p.ji.), giving branches to the extensor muscle {e.^) 

 of the second joint, and ending in the epidermis upon the outer 

 side of the joint. The branches supplying the tergo-coxal 

 muscles represent the ento-coxal branches of a typical neuromere. 



The main cheliceral nerve [i.p.n.) innervates the epidermis in 

 the first, and the flexor muscle (_/.^) of the second joint. Here 

 it gives branches to the skin and to the muscles {e.^ and f.^) 

 which move the third joint, and then divides into two large 

 sensory branches which break up in the chelae to supply the 



