CoGHiLL, Cranial Nerues of Triton. 249 



and enters the m. rectus superior. But in this case, which occurs 

 only on the one side of this specimen, the r. ophthalmicus profun- 

 dus penetrates the m. rectus superior, whereas it usually passes 

 dorsal of this muscle. This peculiarity of the ophthalmicus in 

 this case no doubt explains the exceptional behavior of the r. 

 superior III. 



The r. inferior is less constant than the r. superior in its position 

 relative to the muscles. It is quite as variable in this respect in 

 Triton as in Amblystoma. In Triton the nerve usually passes 

 caudal or ventral of muscle rectus inferior to arrive at the other 

 two muscles. Frequently, however, the r. inferior is penetrated 

 by the proximal portion of the m. rectus inferior and rectus 

 internus. 



As compared with the third nerve of Amblystoma, that of Triton 

 requires special notice, also, with reference to the distribution of 

 nerve cells upon it. The occurrence of these ganglion cells can 

 not be adequately treated, however, without first considering two 

 other important relations of the oculomotor nerve ot Triton, viz: 

 the branch of the oculomotor to the interior of the eye, and the 

 anastomosis of the r. inferior III with a branch of the r. ophthal- 

 micus profundus V. 



The oculomotor branch to the interior of the eye comes off the 

 main nerve in or near its foramen. It follows the general direc- 

 tion of the optic nerve and is partially enveloped in the posterior 

 border of the connective tissue sheath of the optic nerve. It is a very 

 small nerve and its fibers are only faintly medullated till they 

 reach the eye, where they lose their medullary sheaths entirely. 

 After penetrating the sclera the nerve can be traced a long dis- 

 tance around the posterior border of the choroid. In a close study 

 of three specimens I have found no important variation in these 

 relations. 



The anastomosing branch from the profundus usually arises from 

 the main nerve as the latter crosses the oculomotorius. It then 

 turns directly ventrad and joins the r. inferior III. In case the r. 

 superior III arises farther centrally than usual, the communicating 

 nerve has been seen to turn a very short distance centrad on the 

 r. superior and enter the r. inferior. In other cases the communi- 

 cating nerve arises near the Gasserian ganglion. It then becomes 

 a nerve of considerable length, and resembles the corresponding 

 nerve of Amblvstoma. 



