392 Jo'i^ F' Holoi 



The Radix posterior leaves the ganglion at the caudal end, 

 close to the issue of the nerve. The fibres are semi-arched and 

 seem to end in a nucleus of small cells situated about half way 

 between the surface of the Medulla and the Median line. 



The Ramus posterior acustici enters the Medulla a little above 

 the ganglion of the Ramus anterior, runs in a horizontal direction 

 across the restiform body towards the medial surface of the same, 

 turns then in a caudal direction and, running parallel to the surface, 

 ends in the adjoining gray matter and in the Ganglion centrale 

 superior, together with fibres from the Ramus anterior and Trige- 

 minus as before described. 



The absence of any sensory element in the Facialis of Myxine, 

 which corresponds with the sensory Facialis in other fishes and some 

 Amphibians, is probably a primitive condition, as everything indi- 

 cates that the two Acustic nerves are the sensory elements cor- 

 responding to the two motor elements in the Facialis. 



The so-called sensory Facialis, which is found in certain ani- 

 mals whose existence is aquatic and which is connected with a 

 special sense organ (the lateral line of the head) is evidently nothing 

 but a differentiated branch of the Trigeminus and degenerates at 

 the same time as this organ in animals of terrestric life. 



The Ninth Nerve, or the Nervi Glossopharyngeus and Lateralis. 



These nerves are described as being absent in Myxine by all 

 authors on the subject except Sanders (41), who, in describing the 

 Vagus, states that this nerve, after passing over the ear capsule, 

 pursues its course backward between the dorsal and ventral muscu- 

 lar masses »and is therefore the Lateral nerve«. The nerve San- 

 ders has seen passing backward is no doubt the Lateralis, but the 

 Lateralis does not issue from the brain in the way he describes, 

 though his description tallies very well with the manner in which 

 the Vagus leaves the brain. Both nerves are, however, present in 

 Myxine and Sanders' error is explained by the fact that, during 

 its caudal course, the Lateralis is inclosed in the same connective 

 capsule as the Vagus nerves (Fig. 22). 



Stannius (43) describes the Nervus lateralis in fishes as con- 

 sisting of one bundle of fibres springing from tuberosities of the 

 Corpora restiformia. The Nervus glossopharyngeus he believes to 

 be a part of the Vagus in the Cyclostomes and Lepidosiren, but in 



