40 journal of Comparative Neurology and Psychology. 



thorough knowledge of the 'tween-brain centers. It remains to 

 be mentioned that the tr. mesencephalo-lobaris posterior goes from 

 the anterior as well as the posterior part of this nucleus to the 

 region of the nucleus lateralis mesencephali and the tectum. 



The nucleus rotundus proprius (nucleus ventralis thalami of 

 Goldstein) is clearly defined: (i) on account of the peculiar 

 structure of its cells, already referred to by Fritsch who com- 

 pared them w^ith the glomeruli olfactorii, as Bellonci also did; 

 (2) by the way in which the tr. rotundo-lobaris gathers on its 

 periphery. As already mentioned, the com. horizontalis of 

 Fritsch goes through the nucleus rotundus, entering at the in- 

 ferior side and leaving at the top, then bending forward with the 

 tr. rotundo-lentiformis and ending in the nuclear region behind 

 the com. posterior under the ventricle. 



Finally I have still to mention as belonging to the nucleus 

 rotundus proprius a tract which has been mentioned several times 

 before. It is short, but large and strongly medullated and en- 

 wraps the nucleus, covering it, as it were, with a layer of myelin, 



after which it goes into the nucleus subrotundus and the stratum 



.... 

 griseum lohi inferioris proprius and ends there. It is most 



remarkable that I do not find this latter tract, which is so strongly 



developed in Gadus, mentioned either by Edinger or by Catois, 



while it is so excellently represented by Bellonci and described 



by David. C. L. Herrick seems to have seen it, as he speaks of 



"fibers embracing the nidulus from all sides except dorsad," 



which must be the fibers of this tract. 



Now, having mentioned the connections of the nucleus rotundus 

 proprius and having described those of its "Nebenganglien," as 

 Edinger calls them, I must speak further of the substantia grisea 

 lohi inferioris, as I term the rest of the gray substance of the hypo- 

 thalamus, which cannot be regarded as a distinct nucleus and 

 therefore has been justly called nucleus difFusus hypothalami by 

 Goldstein. I have divided this substantia grisea lobi inf. into 

 two parts, both situated in the more inferior, lateral and central 

 parts of the lobi. 



The pars anterior is connected with fibers of the tractus lobo- 

 cinereus brevis, the tractus thalamo-lobaris, or bundle of ViCQ 

 d'Azyr, and the fasciculus intralobaris, while the pars posterior 

 is connected with the tr. olfacto-hypothalamicus (or -lobaris) 

 lateralis, a part of the tr. strio-thalamicus, the fasciculus intra- 



