Kappers, Tcleostean and Selachiajj Bram. 91 



by Johnston for the ganoids. It is not easy, however, to state 

 this with certainty. Nor do we find in Galeus with common 

 methods of investigation a sufficient ground to state these relations 

 near the acoustic field, where in the teleosts the fasciculus longi- 

 tudinalis lateralis terminates after having formed the fibrae 

 arcuatae dorsales. A tract of decu'ssating fibers situated under the 

 ventricle, passing through the fasciculus longitudinalis dorsalis 

 and losing itself in the acoustic field on one side and on the other 

 side in a group of fibers immediately lateral to the dorsal bundle 

 cannot be interpreted as such with aiiy certainty. Though 

 among the great number of fibrae arcuatae ol this region there are 

 many which can be seen to take this course, thib does not give me 

 sufficient evidence to consider them as the homologue of the lateral 

 fasciculus of the teleosts, even though I am personally convinced 

 that it is to be found in the selachians, in which the static center is 

 even more strongly developed than in the bony fishes. 



Happily we can give a clearer report on the tr. thalamo- and 

 tecto-bulhares et spinales, which I shall have to treat of here to- 

 gether, as it is impossible to separate the thalamic and the tectal 

 fibers. After an important part of this group has entered the 

 cerebellum (Figs. Ixx, Ixxi, Plate VI), the remainder terminates 

 partly in the ventral gray layers of the medulla oblongata and in at 

 least equal amount farther backward. 



The gray mass of the oblongata which in Gadus is so clearly 

 seen to begin in the region of the trigeminus and shows its greatest 

 development in the octavus region is in Galeus canis a great deal 

 more diff^usely spread and is differentiated only in the region of the 

 trigeminus (Fig. c, Plate VII) as a more compact scale-shaped 

 mass on both sides of the raphe. In the octavus region, however, 

 it is impossible to distinguish any such local concentration. 



The tracts also extend farther backward and decrease only very 

 gradually giving more fibers also to the nucleus parascptahs which 

 is so strongly developed in the whole vagal region, situated ven- 

 trally beside the raphe (Figs, cvi, cvii, Plate VII). Thereupon, 

 the greater part of the tracts run backward into the spinal cord, 

 where they occupy a lateral and ventro-lateral position. It is 

 especially this spinal part of the whole complex which seems to 

 make this group of fibers so much larger in the selachians. It need 

 hardly be mentioned that it is out of the question to follow the 

 course of any separate tract into the nucleus of the abducens. 



