No. I.] 



STUDIES ON LIMULUS. 



143 



gustatory organs. A large blood vessel accompanies the 

 cheliceral nerve and supplies the appendage with blood. 



(2) The Haemal Nerves. — The non-ganglionated haemal 

 nerves (/.«., h.n.') arise from the haemal side of the neuro- 

 mere. Each nerve passes for- 

 ward, dorsal to the lateral eye 

 nerve, upon the median side of 

 the tergo-coxal muscles of the 

 chelicerae, and there fuses with 

 the haemal nerve {Ji.n) of the 'X- 

 second thoracic neuromere. It 

 soon leaves it, however, and, 

 passing haemal to this nerve, 

 turns posteriorly around the base 

 of the second appendage, keeping 

 close to the median eye nerve. 

 The rest of its course lies in the 

 epidermis upon the neural sur- 

 face of the carapace, outside the 

 bases of the appendages. It does 

 not branch much, if any, until it 

 reaches the skin, just posterior 

 to the sixth leg, beneath a sclerite 



which lies opposite the flabellum. Fig. 10. — Diagram showing muscles and dis- 



H.. . rr 1 r tributiou of nerves in chelicera of adult 



ere it e:ives off a number of Limulus, from the anterior side (natural 



size). /, 2, and 3, first, second, and third 

 joints of chelicera ; ^.'"3, extensors of first, 

 second, and third joints, respectively ; f^^, 

 flexors of first, second, and third joints, re- 

 spectively ; l.nt.^, lateral muscles of first 

 joint ; e?-,/}-, and/.;?/.' constitute the tergo- 

 coxal muscles; h.c, haemal side of the 

 carapace ; br., fore-brain ; tt.n}-, neural 

 nerve or cheliceral nerve ; i.p.n., internal 

 pedal nerve ; e.p.n., external pedal nerve ; 

 h.n^, haemal nerve of cheliceral neuro- 

 mere or lateral nerve. 



branches which ramify over the 

 skin. The main nerve is con- 

 tinued onto the abdomen, where 

 it branches at regular intervals, 

 sending a small fiber toward the 

 bases of the first five abdominal 

 appendages. Opposite the last 

 appendage it breaks up into nu- 

 merous filaments, ramifying over a large portion of the skin in 

 that region. 



It is a noteworthy fact that this nerve branches profusely in 

 the skin beneath a sclerite similar to that in the olfactory region, 

 and also that this sclerite and the flabellum, which is highly 



