Kappers, Teleostean and Selachian Brain. 39 



lobus passes over into the central brain mass (Figs, xliii, li). A 

 part of the libers of this tract pass anterior to the first decussation 

 of the lemniscus, another part between the first and the second 

 decussation, into the base of the mid-brain. Their further course 

 will be treated beyond. 



(2) The second caudal connection is much smaller than the 

 first one and forms the tractus loho-peduncularis, a small bundle 

 containing but little myelin but sharply delineated arising from 

 the pars posterior of the lobi (Figs, xlix and 1) and breaking 

 through the com. ansulata to end in the corpus interpedunculare 

 together with the fasciculi retroflexi. It seems to me that Edin- 

 GER and Catois have described the same bundle as tr. mammillo- 

 peduncularis. 



Nuclei of the Hypothalamus and Adjacent Parts of the Thala- 

 mus. Owing to the course of these tracts and those described 

 before, and also on account of the differences in the cells, one can 

 distinguish several groups of cells in the hypothalamus and adjoin- 

 ing parts of the thalamus. The first group of cells, situated most 

 dorsally, proximally and laterally, is the nucleus prcerotundus. 

 This group is related to the com. transversa and the tr. mesen- 

 cephalo-lobaris anterior and gradually passes backward into a 

 much larger group situated under and lateral to the level of the 

 nucleus rotundus and ending where the real nucleus rotundus has 

 its largest size. This latter group, which belongs entirely to the 

 lobi inferiores, I shall distinguish as the nucleus subrotundus from 

 the nucleus rotundus proprius, as it extends in part under the real 

 nucleus rotundus so that the com. horizontalis, before it enters the 

 lower border of the latter, lies for some distance over it and between 

 it and the nucleus rotundus proprius. It is in the foremost part 

 of this group of cells that the greater part of the tr. olfacto-lobaris 

 medialis terminates, while in its posterior part the greater part of 

 the tr. strio-thalamicus ends, bending downward in the same way. 



Evidently this nucleus subrotundus has always been considered 

 to belong to the nucleus rotundus. Goldstein alone describes 

 it separately in his work and he also states that a part of the strio- 

 thalamic fibers end here. Accordingly, investigators generally 

 have considered most of the above-mentioned tracts to end in the 

 nucleus rotundus; Bellonci his tr. olfacto-rotundus, and others 

 the greater part of the tr. strio-thalamicus. This group of cells 

 must be considered separately if we are ever to obtain a more 



