Kappers, Teleosteau and Selachian Brain. 67 



The /r. lobo-cerehcUaris, whose origin has been described in the 

 second chapter, enters the mid-brain at its junction with the infe- 

 rior lobes and runs backward in its latero-basal part, crossing at the 

 same level as the ansulate commissure and then going upward 

 into the cerebelluiji (Fig. Ixx, Plate IV) between the ascending 

 fibers of the tr. mesencephalo-cerebellaris frontally and the cere- 

 bellar fibers of the lemniscus caudally. This tract is as strongly 

 developed in the selachians as in the teleosts and follows the same 

 course. 



Regarding the fasciculus retroflexus, I have already mentioned 

 that this compact bundle before entering the interpeduncular 

 ganglion divides into three or four smaller bundles which cross 

 the median line at the same horizontal level (Fig. Ixi, Plate IV) 

 and then enter the strongly developed ganglion interpedunculare 

 (Fig. Ixxii). 



The tr. loho-peduncularis is much more difficult to trace with 

 certainty. This tract which is so compact and easily traced in 

 the bony fishes as an uncrossed feebly medullated connection of 

 the posterior and medial parts of the inferior lobes with the corpus 

 interpedunculare has been described by Johnston under the 

 name of tr. mammillo-bulbaris, and sureh' is present in the sela- 

 chians, where we find mesad of the tr. lobo-cerebellaris a very 

 clear unmedullated tract which cannot be followed further than 

 the base of the mid-brain. Though I was not able to see its ter- 

 minus m the interpeduncular body, I am convinced that these 

 fibers represent the lobo-peduncular connection of the bony fishes. 



As for the origin of the oculomotorius and trochlearis, I must 

 mention first that it may be that the greater part of the fiber tract 

 described as tr. mesencephalo-cerebellaris or tecto-cerebellaris 

 superior does not enter the tectum at all, but enters the nuclei 

 of these nerves, representing the similar connection in teleosts 

 and ganoids. The more I investigate this region the more is this 

 impression strengthened, which would find some further support 

 in the fact that the fibers which will be described in the second part 

 of the fourth chapter as tr. cerebello-motorius cruciatus, arise in 

 the same part of the cerebellum as these fibers, have similar 

 heavily medullated sheaths and take the same course. 



I can confirm Catois that the decussation of the eye-muscle 

 nerves is not total, but partial. The oculomotorius leaves the brain 

 at its base and the trochlearis dorsally just anterior to the velum. 



