593 



the granular layer of all three divisions (Figs. 7—11, Tr. tecto- 

 cerehell.). A very large bundle of fibres coming from the Lobi in- 

 feriores by way of the postoptic decussation sends a large part of its 

 fibres into the cerebellum, the remainder passing on to the base 

 of the medulla (Figs. 10 and 11, Tr. loho-hulh. et cerebelL, 

 crossed). A large part of these fibres cross to the opposite side 

 in the ventral part of the cerebellum, forming three distinct medullated 

 commissures posterior to those connecting the secondary vagus nuclei. 

 A smaller bundle of uncrossed fibres from the inferior lobes enters 

 the cerebellum with the crossed fibres (Fig. 11, Tr. loho-cerehell.). 



I have also traced to its ending in the cerebellum the bundle known 

 to the Germans as the Bindearm, but it is not shown in the figures. 



I wish to emphasize the structural continuity of the cerebellum 

 and the tuberculum acusticum. These are not only connected by the 

 distribution of the fibres of the Vth., Vlllth., and lateral line nerves 

 to both, but the nerve elements are the same in both. Every type 

 of cell which is present in the one is represented in the other. There 

 are great differences in detail between various parts (e. g. valvula and 

 acusticum), but these differences are minor modifications. The essential 

 features are the same and the various parts blend into one another 

 by such gradual transitions that we are bound to consider them 

 fundamentally one continuous structure. The cerebellum arises in 

 Teleosts, as Schaper ('94) has shown, from the lateral parts of the 

 anterior end of the medulla. In those forms in which the cerebellum 

 is simplest, as Protopterus (Burckhardt '92) and the Urodeles 

 (Fish '95), the median portion of the cerebellum is largely com- 

 missural, i. e. it corresponds to that part of the cerebellum in fishes 

 known as the fimbria. These facts point strongly to the conclusion 

 that the cerebellum is the enlarged anterior end of the center for 

 sensory nerves of the integument. Its size in different vertebrates is 

 correlated with the relative importance of the integumentary sense 

 organs, the size of the fibre tracts entering from the tectum, inferior 

 lobes and higher brain centers, and the multiplication of cells of the 



II type to serve the functions of association and coordination. A close 

 relationship between the cerebellum and medulla as indicated by their 

 grosser structure has been noted by Goronowitsch and Kingsbury. 



Certain peculiarities in connection with the dendrites of the Pur- 

 kinje cells deserve attention. In the acusticum, including the L. lineae 

 lateralis, nearly always, and frequently in the cerebellum, the Purkinje 

 cells bear one or more dendrites which are devoid of the little spines 

 which give to the other dendrites their rough appearance. Such cells 



Anat. Anz. XIV. Aufsätze. 41 



