96 'Journal of Co?nparative Neurology and Psychology. 



clearly seen. The left side of these figures, which lies somewhat 

 farther caudad than the right, shows that a part of the motor root 

 fibers before turning upward run backward for some distance along 

 with the tr. descendens nervi qumti as a small cap on the outer 

 side of this tract which can be distinguished from the trigeminus 

 fibers by its darker color. Later it turns upward and terminates 

 partly decussated and partly uncrossed in the motor facial nucleus. 



Kingsbury also stated that fibers of the tr. descendens N. quinti 

 in ganoids leave the medulla with the facialis root. I suppose, 

 however, that he took them for spinal (and sensory) fibers. That 

 this is not the case is proved by the origin of the dark cap on this 

 tract in the motor facialis region and the origin of the fibers which 

 have a thicker and darker colored medullary sheath like those from 

 the motor facialis nucleus. By reason of this course of motor 

 facialis fibers the tr. spinalis N. quinti grows thicker in the region of 

 the motor facialis nucleus and when leaving this region decreases 

 again, in the proportion of about 5:6:5. That such a course 

 exists also in the teleosts I have mentioned before, but there these 

 fibers are not situated dorso-laterallv but ventro-laterally of the 

 descending fifth tract. 



These, however, are not all of the motor fibers. Nearly as large 

 a part immediately runs dorsad, passes for some distance beneath 

 the ventricle and finally terminates in the same place as those just 

 described. The latter part is the homologue of the motor facialis 

 bundle which, in Gadus, forms the larger part and was first 

 described by Van Gehuchten in Trutta (in its different parts as 

 branche interne, ascendente and externe). In the selachians, as 

 in the bony fishes, the motor nucleus lies nearer the floor of the 

 ventricle than the nucleus abducens. 



The sensory facialis originates exactly as in other animals in 

 the anterior part of the communis region, then passes frontad for 

 a short distance immediately under the ventricle somewhat more 

 dorso-laterally than the motor fibers. After their exit from the 

 brain the fibers run into the ganglion geniculi so that this bundle 

 represents the pars intermedia Wrisbergn of the higher vertebrates. 



Green, following Stannius, described in the selachians (includ- 

 ing Galeus canis) three nerves which originate from this ganglion, 

 the ramus palatinus, ramus . praetrematicus and a third branch 

 which runs between the two others along the anterior border of the 

 spiracle and then downward, forward and inward under the mu- 



