6 Journal of Comparative Neurology. 



parallel with the limitans interna and immediately beneath the 

 row of Purkinje cells, to its destination. In the preparation 

 upon which figure i is based I succeeded in following such an 

 axis-cylinder a considerable distance. In this way the 

 neuraxons of those Purkinje cells situated in the cerebellar 

 plate where a granular layer is lacking furnish the principal 

 contingent of the often considerable mass of parallel fibers 

 interposed between the layer of Purkinje cells and the limitans 

 interna. But even where there is a granular layer, the axis- 

 cylinder does not as a rule immediately sink into this ; but first 

 proceeds a short distance in a horizontal direction and then 

 takes a sharp bend inward (fig. 2). It is now to be noted 

 that I never succeeded in any of my preparations in demon- 

 strating collaterals of the axis cylinders of the Purkinje cells, 

 although, as far as I know, their presence has been established 

 in all other vertebrates hitherto investigated. Whether we 

 have here a defective impregnation or whether these collaterals 

 are actually absent in the Selachii, and their absence is perhaps 

 the expression of a lower phylogenetic stage of development, I 

 do not venture to decide at present. Sauerbeck likewise does 

 not mention collaterals in his article. Among his figures of 

 Purkinje cells, however, are some with divided axis-cylinders. 

 May one of these branches represent a collateral ? 



Nerve-cells of the Molecular Layer. 



These cells are for the most part uncommonly delicate and 

 vary extraordinarily in the form and size of the cell-body as well 

 as in the mode of branching of their protoplasmic processes. 

 To properly illustrate this variety of form I have represented a 

 larger number of cells in Plate I, figures 3 to 8. They lie in all 

 levels of the molecular layer, from the layer of Purkinje cells 

 (even pressing in between these) to close to the surface. The 

 rule seems to obtain that the smaller the cells and the shorter 

 their dentrites, the closer they lie to the surface and z'ice versa. 

 The dendiitcs display in general the tendency to extend towards 

 the surface, although in the deeper lying cells there is also a 

 considerable extension of the same horizontally (Plate I, Fig. 3). 



