8 



second V naeiens according to his description is located in the caudal 

 elongation ot' the first, is not completely separated from it and 

 consists of smaller cells, which description is perfectly in accordance 

 with the two V nuclei (see Fig. 3) of which the second, con- 

 sisting of smaller cells and not completely separated from the frontal 

 nuciens, gives also rise to the VII root. (Comp. also Fig. 4—7). 



Like Holm we were first inclined to consider the second (caudal) 

 nucleus only as a VII nucleus, but a more scrutinous examination 

 of the V fibres showed that in this nucleus also the second motor V 

 root found its origin. 



Summarizing we state that the motor V nuclei mentioned by 

 Holm are no motor V nuclei, and that of the two VII nuclei 

 mentioned by this author the frontal one is a pure V nucleus, 

 whilst the caudal more parvocellular one contains root cells of 

 the V and VII. 



This union of motor V cells and VII cells is in perfect harmony 

 with the condition found in Petromyzon (comp. Fig 1). where the 

 motor VII cells also form the caudal contiuuation of the V nucleus 

 and are a little smaller. 



Since we onlj wish to deal with the motor nuclei in this de- 

 scription, we shall pass the acustico-lateral system, which for the 

 American Myxinoid Bdellostoma dombeyi has been so minutely 

 described by Ayers and Worthington ^) and proceed to the motor 

 X nucleus of Myxine. 



It is obvious that, without an examination of the periferal nervous 

 system and its muscles, the question of the presence or absence of 

 a motor glossopharyngeus cannot be settled. 



We can only state that our researches show a reduction of the 

 liuniber of root fibers of the motor X group, which in Myxine only 

 consists of 3 of 4 rootlets, whereas in Petromyzon it contains 

 together with the glossopharyngeus at least 5 rootlets. 



This combined with the fact that the posterior visceromotor column 

 has suffered a reduction in its frontal part is in harmony with the 

 opinion defended by Johnston ') that the glossopharyngeus and perhaps 

 even the first motor X root sensu strictiori are either very much 

 reduced or absent. A comparison of Fig. ia and 2a shows that this 

 reduction is only probable for the frontal pole of the column, 



1) Ayers and Worthington : They finer anatomy of the brain of Bdellostoma 

 dombeyi. I. The acuslicolaleral system.. American Journal of Anatomy Vol. VllI, 

 1908. 



-) Johnston : Note on the presence or absence of the glossopharyngeal nerve 

 in Myxinoids. Anatomical Record Vol. U, 1908, 



