The finer Anatomy of the Nervous System of Myxine glutinosa. 385 



way resemble the motorcells of Myxine but are somewhat smaller 

 (Fig. 8) than some of the other motor cells. 



In Petromyzon Ahlborn (2) found that the Oculomotor nerve 

 sprang from a ganglion of small cells situated close to the base of the 

 brain laterally to the medial line. These cells are irregularly arrang- 

 ed and not larger than the cells of the gray matter, but stain in a 

 peculiar and different manner to these and exactly like those of the 

 motor Trochlearis or the transverse trigeminal nucleus. The rela- 

 tively primitive arrangement in Petromyzon, and the similarit}' in the 

 position and staining properties of these ganglia in Myxine and 

 Petromyzon, make it highly probable that the triangular cells which 

 I observed in the region of the Ganglion interpedunculare are 

 remains of the Oculomotor ganglion. On the base of his researches 

 in Salmo and Scyllium, Haller (17) pronounces the Oculomotorius 

 to be the first independent metaraeric cranial nerve and its absence 

 in Myxine would then undoubtedly be a sign of degeneracy, a degene- 

 racy produced by the optic organs remaining in such a low state 

 of development that a motor apparatus for the eye has not been 

 wanted. 



All investigators on the subject have pronounced the Trochlearis 

 and Abducens to be absent and my own observations confirm this 

 opinion, but their absence need not to be a sign of degeneracy, as it 

 is by no means proved that these nerves represent independent me- 

 tameric cranial nerves, on the contrary, according to the investigations 

 of B. Haller (17), the Trochlearis is to be considered as a dififeren- 

 tiated part of the first Trigeminus; the Abducens, however, he thinks 

 might possibly be a reduced but independent cranial nerve. Still, 

 this is not proved and in Myxine it is probably undifferentiated from 

 the Trigeminus. 



The Fifth Nerve or the Trigeminus. 



The Trigeminus is by far the most conspicuous of the cranial 

 nerves and its ganglion, the »Gasserian ganglion« is of elongated 

 form and is situated laterally along the Encephalon, reaching from 

 the rostral part of the Corpora restiformia to the olfactory lobe. 

 The nerve divides into three branches, the third of which Fürbringer 

 (12) identifies as the Ramus ophthalmicus. The peripherical distribu- 

 tion of the Trigeminus in Myxine has been thoroughly investigated 

 by J. Müller (27), but only one account (a short one by Sanders [41]) 



