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Mr. A. Sanders. On the Anatomy of the [Jan. 7, 



occupies about two-thirds of the thickness, and consists of longitudinal 

 fibres which are derived from the optic tract, and numerous cells 

 which attain tbeir maximum number in this layer; they are mostly 

 spherical, but fusiform cells with their long axes placed radially are 

 occasionally found. 



The second layer consists of bundles of transverse fibres partly 

 derived from the lateral columns of the medulla oblongata, and partly 

 from the commissura ansulata ; they correspond with the transverse 

 fibres in the tectum lobi optici of the Teleostei. 



The third layer is characterised by large cells, which are rounded 

 or sometimes pyriform ; they usually give off only one process which 

 is directed outwards, and joins the above-mentioned transverse fibres. 

 These cells differ in their arrangement in the different species, they 

 are spread out in a fiat layer in the optic lobe of the Scyllium and 

 Raja. In Rhina and Acanthias they form a group in the central 

 tuberosity that projects into the aqueduct of Sylvius, resembling the 

 arrangement in the Turtle. The small cells which were described in 

 the first layer extend in diminishing numbers into this third layer. 



The cerebellum in Scyllium,. Rhina, and Acanthias presents a very 

 large ventricle which in Raja is nearly obliterated ; the intimate 

 structure resembles that of the Teleostei. There are the four layers, 

 the molecular with Purkinje cells, the granular and the fibrous layers. 

 The latter is connected by the crura cerebelli ad medullam through 

 an inferior lobe with the restiform bodies of the medulla oblongata ; 

 there is also an anterior cord passing longitudinally into the optic 

 lobe which represents the crura cerebelli ad cerebrum (Quain). In 

 the granular layer,, in addition to the numerous cells forming that 

 layer, there are little masses of fibrillse inextricably wound together 

 resembling glomeruli on a small scale ; in other respects there is 

 nothing peculiar in the structure of the cerebellum. 



The molecular and the granular layers are continued on the surface 

 of the restiform bodies in all the species examined, and in Raja nearly 

 as far as the posterior end of the fourth ventricle, but the absence of 

 the Purkinje cells marks a difference of structure. 



In the spinal cord the grey substance of the ventral cornu contains 

 numerous large cells arranged in am imbricated manner with their 

 long axes directed obliquely from the ventral to the dorsal surface. 

 Their shape is generally elongated, and they give off several processes. 

 In the cord the ventral cornua are directed horizontally, but towards 

 the posterior end of the medulla oblongata they are gradually depressed 

 toward the ventral surface, and are finally lost in the grey substance 

 on the floor of the fourth ventricle. The dorsal cornua contain 

 numerous nuclei. There are four longitudinal columns in the spinal 

 cord, the ventral longitudinal columns beneath the central canal, the 

 lateral columns at the sides, and the dorsal columns above. Mauthner's 



