266 C. JUDSON HERKICK 



thalami and even still farther dorsally in the pars intercalaris 

 diencephali. Similar dendrites from neurons of the pars ven- 

 trahs thalami extend dorsally among the fibers of this system. 

 This arrangement suggests relations analogous with those of 

 the 'corpus glomerosum,' or nucleus rotundus of Fritsch, with 

 the nucleus anterior thalami, as described by V. Franz ('12, 

 pp. 426-431) in fishes. 



19. Tr actus dorso-ventralis thalami 



Short, slender axons, to which this name is applied, pass 

 directly from the pars dorsalis to the pars ventralis of the thala- 

 mus. Many of them at their origin (figs. 58, 68, tr.d.v.th.) 

 are mingled with fibers of the tractus thalamo-peduncularis 

 dorsalis profundus. They really are of the same type as the 

 latter tract and hardly merit a separate name. 



20. Tractus mamillo-peduncularis 



The hypothalamus has not been exhaustively studied. At 

 the rostral end of the commissure of the tuberculum posterius 

 there is a decussation of hypothalamic fibers, the decussatio 

 hypothalamica posterior; and there are fibers passing backward 

 from the pars dorsalis hypothalami into the motor tegmentum 

 which probably constitute the tractus mamillo-peduncularis and 

 are so designated on the figures (figs. 8, 9, 29, 30, tr.7nam.ped.). 

 None of these connections have been fully demonstrated. In 

 figures 46, 47 and 49 there is shown a collection of peculiar fine 

 varicose terminals laterally of the tuberculum posterius and 

 fovea isthmi which probably belong to this system and are 

 provisionally so designated They make their appearance in 

 the preparations close to the stratum griseum dorsally of the 

 cell bodies of the more medial part of the pars dorsalis hypo- 

 thalami, and they pass directly caudad mingled with dendrites 

 of the neurons of the tuberculum posterius and adjacent parts. 

 Some of them cross in the ventral commissure both above and 

 below the fovea isthnn, and some of them reach the chief terminal 

 nucleus of the tractus habenulo-peduncularis below the fovea. 



