No. I.] STUDIES ON LIMULUS. 173 



nerve have been found opposite the five posterior pairs of ostia. 

 The stump of the cardiac nerve found in the fifth neuromere 

 would then correspond to the rudimentary ostia (r.os). 



c. Nerves of the Alimentary Tract. 



(i) The Rostral Nerves. — Three rostral nerves, a median 

 and two lateral ones (Pis. VI-VIII, and X, Figs. 1-3, 11, and 

 12, l.a.n.), arise from the anterior commissure and innervate the 

 rostrum, or upper lip. 



(2) Stomodaeal Nerves. — A pair of stomodaeal nerves (Pis. 

 VIII and X, Figs. 3, 11, and 12, st.n) arise from large ganglia 

 on the inner side of the oesophageal collar and innervate the 

 oesophagus, proventriculus, and pyloric valve. These have 

 already been fully described under the Nerves from the Mid- 

 Brain. 



A small ganglion upon the sides of the proventriculus, the 

 existence of which is doubtful, has been described by Milne- 

 Edwards. " Au point ou cet organe se replie brusquement pour 

 se porter en arriere, se trouve un tres-petit ganglion aplati, 

 loge, comme le nerf dans I'artere, pres de I'anastomose de cette 

 derni^re avec la branche gastrique eman^e de la convexite de la 

 crosse aortique." The point mentioned is a place within the 

 aortic arch from which several nerves diverge to supply the 

 proventriculus, and where white blood clots are extremely liable 

 to lodge. In alcoholic specimens these clots take on the 

 appearance of ganglia. 



" De ce ganglion partent en avant des filets qui se distri- 

 buent aux parois tres-musculeuses de I'estomac, et en arriere 

 deux rameaux dont I'un se rend a la portion pylorique de ce 

 viscere, et I'autre gagne I'intestin. Ces parties son tres difficiles 

 a distinguer, car elles sont extremement greles, et pour les 

 degager des arteres ou alles sont logees, il faut proceder avec 

 un tr^s grand soin." I have found branches running onto the 

 anterior end of the intestine, but could not trace them beyond the 

 pyloric valve even with a methylen blue stain. Although 

 good stains of the nerves of the proventriculus and the anterior 

 end of the intestine were easily obtained by this method, every 



