Johnston, The Bt'ain of Petromyzon. 77 



as motor cells. They do not arise from the spindle cells of the 

 acusticum and do not decussate. 



3. The nucleus funiculi is diffuse, but recognizable as a 

 special nucleus. 



4. The nucleus funiculi is continuous cephalad with both 

 the nucleus trigemini spinalis and the tuberculum acusticum. 

 Those together represent the acusticum in Acipenser. 



5. The acusticum is covered externally by a cerebellar 

 crest as in selachians and ganoids. 



6. The acusticum and cerebellar crest are continuous 

 with the granular and molecular layers o( the cerebellum, 

 respectively. 



7. There is a lobus lineae lateralis homologous with that 

 of Acipenser and selachians. In Petromyzon it is evident that 

 this lobe is essentiall}/ a part of the acusticum. 



8. The nucleus funicucli, nucleus trigemini spinalis (?), 

 acusticum, and cerebellum have in common two chief types of 

 cells which are characteristic of these centers in fishes and of 

 the cerebellum in higher forms : namely, large cells which are 

 either Pukkinje cells or the forerunners of Purkinje cells, and 

 granule cells. 



g. The VIII root fibers end in the cerebellum, acusticum, 

 and nucleus funiculi; those of the lateral line VII end in the cere- 

 bellum and acusticum ; those of the V in the cerebellum, acusti- 

 cum (?), nucleus trigemini spinalis, and nucleus funiculi. 



10. The presence of lateral line organs is confirmed. 

 These are numerous pit organs arranged much as in other fishes, 

 and the special cutaneous center in the medulla is corr'espond- 

 ingly large. 



11. There is a large post-auditory lateral line root which 

 forms the greater part of the lateral line nerve and gives a com- 

 ponent to the trunk of IX. 



12. The VII-X anastomosis is composed almost exclu- 

 sively of lateral line components. It receives a few communis 

 fibers whose destination is unknown. 



13. The N. lateralis is a true lateral line nerve, receiving 



