188 J. B. JOHNSTON, 
layer have short neurites and are to be compared with the small 
cortical cells of man. In the granular layer are small and large 
granule cells. The small are like those of Teleosts. Their neurites 
enter the molecular layer. Here SCHAPER has not been able to 
trace them to the T-branching characteristic of these fibres in all 
other Vertebrates, but he is convinced that certain T-branchings 
which he figures are the same as those in Teleosts. His figure sug- 
gests to me rather that he has to do with collaterals given off at 
right angles from the main fibre in its horizontal course, and not 
the main fibre giving rise to two horizontal branches. SCHAPERS 
failure to trace these fibres to their T-branching taken with my 
failure to find such branching in Acipenser, suggests that in Selachians 
and cartilaginous Ganoids these fibres do not branch as they do in 
higher Vertebrates. My preparations have given me splendid op- 
portunities for finding these branchings, especially in the region of 
the commissure (fimbria), where they should certainly be found if 
they exist at all in Acipenser. The large granule cells in Selachians 
are cells of the II type. The very large size of the cell bodies and 
the coarseness of the dendrites makes it difficult to compare them 
with the II type cells which are so numerous in Acipenser. SCHAPER 
says that the cell body “in size often exceeds that of the PURKINJE 
cells”. If by this he means to compare them with a restricted 
portion of the body of PuRKINJE cells, such as appears in my 
photographs or in fig. 2 of his Anzeiger paper on Teleosts, then the 
same might be said of the largest of the II type cells in Acipenser. 
This can scarcely be his meaning since the PuRKINJE cells which 
he figures in Selachians have large compact bodies. I have described 
two or three varieties of II type cells in the granular layer in Acı- 
penser, and it may be that these cells are subject to considerable 
variation, of which the large cells in Selachians are an extreme 
example. 
In a recent paper SCHAPER (99) points out the presence of the 
characteristic molecular and granular layers and PURKINJE cells in 
the cerebellum of Petromyzon. 
SCHAPER’s treatment of the afferent fibres to the cerebellum is 
very unsatisfactory. Whether from imperfect impregnation or from 
working on sections made from small pieces of brain tissue, he was 
able to recognize only a few afferent fibres, In Selachians he 
identified only one such fibre with certainty, although in Teleosts 
he gives a more extended description as quoted above. In all cases 
