310 



homologiziiig the ampullae with the end buds falls to the ground 

 utterly. 



The nature and homology of the "Lobus trigemini" in selachians 

 and ganoids, and its relation to the fasciculus communis centers in 

 teleosts, are perfectly clear from the works of Stannius (11), Mayser (9) 

 and GoRONOwiTSCH (3), and the confusion which has arisen from the 

 use of the term "Lobus trigemini" in two senses by the last two 

 anthers is wholly inexcusable. Briefly the facts are as follows: 



Stannitjs recognizes: 



a) a lobus medullae oblongatae sive posterior which 

 serves in teleosts as the center for the N. lateralis, Rr. laterales VII, 

 and VIII; 



b) a most dorsal ridge called a part of the Corpus resti- 

 forme, which is present in elasmobranchs and Acipenser dorsal to 

 the lobus posterior, and receives the lateral line VII rami; 



c) coarse fibred sensory roots from the above centers and a fine 

 fibred root caudal to the coarse fibred, which forms the R. palatinus 

 VII, etc. 



Mayser describes the "Lobus trigemini s. impar" of teleosts as 

 continuous with the cephalic end of the lobus vagi, and states that it 

 gives rise to the "N. Vgen. dors." which runs forward and outward 

 through the tuberculum acusticum. It is evident that this "Lobus 

 trigemini" is the same thing as the front end of the lobus vagi in 

 Acipenser as described by Gorono witsch , and that the N. V gen. 

 dors, is the dorsal VII {Frd. of Goronowitsch, fasciculus communis 

 VII of Strong). 



Goronowitsch uses the term "Lobus trigemini" for a lobe or 

 ridge lying above the acusticum from which arises a coarse fibred sen- 

 sory root, his "Trig. II dors." It is evident that this is the most 

 dorsal lobe mentioned by Stannius in selachians as a part of the 

 Corpus restiforme. 



In an earlier paper by the writer (4) to which Allis makes re- 

 ference, the nature of the so-called lobus trigemini in Acipenser is 

 discussed and evidence given to show that it is not a separate nerve 

 center but is a part of the tuberculum acusticum. It was stated that 

 "a considerable number of fibres entering the acusticum in the ventral 

 of the two [lateral line VII] roots pass directly around the inner side 

 of the cerebellar crest and enter the so-called L. trigemini. The mi- 

 nute structure of the L. trigemini is identical with that of the acusti- 

 cum, and both are directly connected anteriorly with the granular 

 layer of the cerebellum. Both also bear the same relations to the 



