The brain of Acipenser. 239 
IV. Summary of Results. 
1) The review of the literature of the cranial nerves shows that 
since the work of STRONG, COLE, and HERRICK both the central 
relations and the peripheral distribution of all the chief components 
are known. The V nerve is general cutaneous and components of 
this system run also in the roots of the IX and X nerves. The 
lateral line VII and X supply canal organs (typical and modified). 
The central relations of the lateral line and VIII nerves add support 
to the hypothesis that the ear is derived from canal organs. The 
VII, IX and X nerves make up the fasciculus communis system 
which supplies viscera and the end buds both in the mouth and on 
the surface of the head and body. 
2) The study of their minute structure and connections shows 
that the centers for the V, VIII, and lateral line components are 
intimately related morphologically. The close similarity of structure 
argues that they have had a common origin, and it is possible in 
Acijenser to trace the peculiar structures of the acusticum and cere- 
bellum, notably the PURKINIE and granule cells, back to simpler 
elements such as exist in the dorsal horns of the cord. All these 
centers are intimately bound together and it is reasonable to con- 
clude that they have been differentiated from a common fundament 
in primitive Vertebrates which was the direct cephalic continuation 
of the dorsal horn. 
3) The V, VIII, and lateral line nerves all send a part of their 
root fibres to the nucleus funieuli. The VIII and lateral line fibres 
end in part in this nucleus and in part in a special nucleus mesial 
to it. This tract and its special nucleus are homologous with the 
spinal VIII tract and nucleus in man. The fact that the nucleus is 
only partially separated from the nucleus funiculi is additional 
evidence for the morphological unity of the dorsal horn and the 
acusticum. 
4) The lobus lineae lateralis (“Lobus trigemini” of GORONO- 
WITSCH) is shown by its structure to be an integral part of the 
acusticum. 
5) The cerebellum has been developed from the cephalic end 
of the acusticum. The acusticum and cerebellar crest are to be 
compared directly with the granular and molecular layers of the 
cerebellum, respectively. The degree of development of the cere- 
bellum is related to the activity of the animal. The correlation, 
