Kappers, Teleosteo77 and Selachian Brain. ^ 65 



the colliculus of the teleosts has been derived, /. .?., in the place 

 where the tectum is attached to the ventral wall and in the deep 

 layer of the tectum itself. In connection with this deduction, two 

 facts are very interesting: first, the great radial dimensions of the 

 roof, especially the broad base by which the tectum is inserted 

 on the ventral wall of the mid-brain in the selachians as compared 

 with the teleosts {cf. the figures of the tectum of the two fishes); 

 and, second, the fact that Johnston found a tract ending in the 

 tectum of the ganoids (where the colliculus, moreover, is very 

 small), which in the teleosts certainly does not end there, his tr. 

 bulbo-tectalis, my fasciculus lateralis, the secondary acoustic 

 tract. 



I cannot leave the description of the tectal attachments without 

 mentioning a tract which Edinger has also described in his publi- 

 cation on the cerebellum, and which he calls the tr. cerehello- 

 tectaltSy a connection of the cerebellum with that part of the lobi 

 optici in which the nucleus magnocelliilaris tecti is found (Figs, liv 

 to lix). This particular nucleus has already been mentioned by 

 RoHON and Sanders. The former did not make any mention 

 of its neurites, but Sanders described their axis cylinders as 

 running over the median line in the lamina commissuralis tecti. 

 HousER gives an extensive description of its cells and also records 

 that not all of their neurites take their course over the median line. 

 He is of the same opinion as P. E. Sargent that the most anterior 

 fibers of this nucleus enter into the aqueduct and afterward into 

 the sinus rhomboidalis, thence backward into the medulla spinalis, 

 while the most posterior cells of this group form the cerebellar 

 tract mentioned. 



I have not seen these intra-ventricular fibers, nor even one of the 

 neurites turned in the direction of the optic ventricle, but can state 

 clearly that almost all of them cross the median line and mingle 

 with the fibers of the deepest layers of the tectum. I do not know 

 whether they afterward run into the cerebellum as Houser stated 

 for these fibers and as Edinger and Johnston think possible, 

 forming the tr. tecto-cerebellaris which disappears in the velum 

 anticum. But it is quite certain that a tract of a few thick and 

 strongly medullated fibers is easily to be distinguished in the 

 velum crossing there and running forward and then going upward 

 into the deep layer of the tectum. This is as described by John- 

 ston for the ganoids save that he does not speak of a decussation 



