No. I.] 



STUDIES ON LIMULUS. 



155 



divides into three main branches, the external, median, and 

 internal, opercular nerves {e.o.n., m.o.it., and i.o.n.). 



The first of these {i.o.n.) again divides into a motor 

 and a sensory branch ; the motor branch innervates the large 

 abductor muscles (ab.m.^) upon the anterior face of the append- 



FiG. 14. — Diagram showing the muscles and nerves of the chilaria of Limulus, from anterior side. 

 The appendages are revolved outward about 45° (magnified nearly ij^ diameters). 



b.c.'', capsuliginous bar or branchial cartilage ; endo., endocranium ; k.c, haemal side of 

 carapace; ht., heart ; int., intestine; oc.r., occipital ring; p.s., pericardial sinus. 



Muscles: 7 *-e, plastro-coxal muscles; 7 f and g, tergo-coxal muscles; i.m., inter-tergal 

 muscles; v.p.tn?, veno-pericardiac muscles. 



Nerves : h.n.^ and ^, haemal nerves of chilarial and opercular neuromeres ; i.ny , intestinal 

 nerve ; in.nj and ^, integumentary branches of haemal nerves of chilarial and opercular seg- 

 ments ; l.c.n., lateral cardiac nerve ; l.s.ti., lateral sympathetic nerve ; in.c.n., median cardiac 

 nerve ; «.«.' and ^, neural nerves of chilarial and opercular neuromeres; /., pericardium ; 

 s.c.n.^ and *, fused segmented cardiac nerves of chilarial and opercular neuromeres. 



age, and the sensory branch supplies the epidermis of the 

 anterior face and outer margin of the base of the appendage. 



The second branch (tn.o.n.) also divides into a motor and a 

 sensory branch ; the motor branch supplies the external bran- 



