No. I.] STUDIES ON LIMULUS. 147 



{{.man.) and its flexor muscle {/.'"), and then breaks up into fine 

 branches, which ramify over the posterior surface of the man- 

 dible [vtan.) and innervate some of the gustatory spines. The 

 second branch supplies the anterior surface of the mandible and 

 the more anterior of the gustatory spines. The third branch 

 innervates the outer portion of the mandible and sends some 

 fine branches to the skin of the inner proximal portion of the 

 basipodite {2-bas.). 



In the second appendage the first mandibular branch is much 

 reduced in size and innervates only the inner portion of the 

 mandible. There is no inner mandible and, consequently, no 

 corresponding nerve. The second mandibular branch is enlarged 

 and innervates the greater part of the mandible upon both the 

 anterior and posterior sides. The third branch is about as in 

 the third appendage. 



In the fourth and fifth appendages there are only two man- 

 dibular branches, each with a ganglion near the base. The 

 first one, however, divides into three branches, one to the inner 

 mandible and its flexor muscle, one to the posterior, and one to 

 the anterior side of the mandible. The second ganglionated 

 mandibular branch has a distribution similar to that of the third 

 branch in the third appendage. It is evident that the ultimate 

 distribution of the mandibular branches of these appendages is 

 the same as in the third, but the mode of branching at their 

 bases is a little different. 



In the sixth appendage (Text-fig. 12) there are only two man- 

 dibular branches {m.n). The first is not ganglionated and is 

 much reduced. It divides into three branches, which are dis- 

 tributed to the inner portion of the mandible, where there are 

 no gustatory spines. The second mandibular branch is gan- 

 glionated and corresponds to the third branch in the third 

 appendage. It divides into two portions, one supplying the 

 outer part of the mandible upon which there are a few spines, 

 and the other supplying the inner proximal portion of the 

 basipodite. 



(b) Ento-coxal Branches. — In the third appendage (Text-figs. 

 9 and 1 1 ; PI. VII, Fig. 2) there are three ento-coxal branches, an 

 anterior {a.e.n), a posterior {p.e.n), and a median one {m.e.n.). 



