No. I.] STUDIES ON LIMULUS. 179 



of the proximal portion of the appendage, and one to the distal 

 portion ; the haemal nerve arises from the anterior side of the 

 abdominal ganglion and divides into three branches : (i) the 

 intestinal branch ; (2) the cardiac branch ; and (3) the integu- 

 mentary branch. 



7. The rostrum, oesophagus, and proventriculus are inner- 

 vated by the rostral and stomodaeal nerves, which arise respec- 

 tively from the pre-oral commissure and from the ganglia on the 

 median sides of the first thoracic neuromere. 



The intestine and rectum are innervated by the intestinal 

 nerves, which arise from all the neuromeres from the sixth to the 

 sixteenth (possibly from the second also). 



The intestinal branches of the sixth to the sixteenth neuro- 

 meres anastomose with each other and form plexi or longitudinal 

 connectives parallel to the ventral cord. 



8. The heart extends through all the metameres from the sixth 

 to the thirteenth and is probably innervated by cardiac nerves 

 from each of the neuromeres from the sixth to the thirteenth, 

 although actual connections have been made out only in the five 

 branchial neuromeres, viz., the ninth to the thirteenth. 



The cardiac branches of the vagus and abdominal neuromeres 

 are joined to each other by longitudinal connectives or sympa- 

 thetic branches, viz., the lateral sympathetic and the pericardial 

 nerves. 



9. The muscles of each metamere are innervated from the 

 corresponding neuromere. If the muscles of several metameres 

 become fused with one another, the nerves of the different 

 neuromeres anastomose with each other to form plexi. 



10. The chilaria were regarded by Owen and Lankester as 

 detached inner portions of the sixth pair of mandibles. This 

 is without doubt an error, since in the embryo there is a separate 

 neuromere for the chilaria, and in the adult, though the ganglia 

 are fused with those of the sixth and eighth neuromeres, there 

 is still a pair of distinct neural (fi.ny) and haemal nerves 

 {h.nJ) belonging to the chilarial neuromere. The appendages 

 also have a complicated set of muscles of their own, both plastro- 

 coxals and tergo-coxals. 



Moreover, the chilaria have certain characters which place 



