OF DENISON UNIVERSITY. 4 1 



are occupied chiefly with fibres, especially ectad. There are also 

 scattered cells lying laterad and ventrad of the nidulus of the habena, 

 which stain very feebly. These are multipolar or bipolar, with occa- 

 sional flask-cells like those of the rest of the thalamus. Meynert's 

 bundle enters this nidulus from behind. This seems to be what has 

 been described in Vol. V of this bulletin, page 76, as the nidulus of 

 Meynert's bundle, though differing considerably in form and position 

 from the arrangement there presented. This nidulus of Meynert's 

 bundle has also been described in reptiles, though there much further 

 caudad and ventrad.* 



The fibres of Meynert's bundle pass caudad beneath the taenia re- 

 ceiving some fibres from the latter, as far as the superior com- 

 missure. At this point they turn abruptly, pass caudo-ventrad through 

 the thalamus, cross the fibres of the third nerve near their exit, and 

 disappear. The taenia thalami pass cephalo- ventrad from the eras of 

 the epiphysis, lying dorsad of the median, denser cell-cluster, or nidu- 

 lus of the habena. They take the usual course, passing ventrad and 

 laterad and at least at first somewhat caudad behind the anterior com- 

 misure, soon to be lost among the peduncular fibres. 



The Commissural Apparatus of the Habena and Optic Lobes. In 

 this region there are two commissural systems, the first cephalad, the 

 second caudad of the epiphysis. The first system comprises the superior 

 commissure and the commissure of the habense. These commissures 

 are distinct in the lizard, f but in these types are fused. The whole 

 may here be called the superior commissure. It is horseshoe shaped, 

 the convexity being caudad and dorsad. Plate II, Figs. 9 to 12, illus- 

 trates these commissural systems in Geomys. Fig. 10 shows fibres from 

 the lateral parts of the habense arching caudo dorsad toward the me- 

 son, which, however, they do not quite reach at this level. Fig. 11 



:; C. L. Herrick, "Topography and Histology of the Brain of Certain Rep- 

 tiles," Journal of Comparative Neurology, Vol. I, p. 26. 



"If the superior projecting portion of the habena surrounding the base of 

 the stalk of the epiphysis be considered the habena proper, the deeper and more 

 ventro-caudad portion maybe distinguished as the nidulus of Mynert's bundle, 

 or nidulus Meynerti. The fibres of Meynert can be traced to the portion men- 

 tioned (which in the black snake forms a distinct nidulus.) The cells are rather 

 larger than those of the habena, and less compactly clustered about the walls of 

 the third ventricle extending some distance ventrad." 



|C. L. Herrick, loc. cit. 



