RECONSTRUCTION OF LEMUR MONGOZ 8i 



extends for some distanee mesially under the subependymal layer of the 

 central gray matter of the fourth ventricle. It lies immediately dorsal to the 

 vestibular nuclei, separating this mass from contact with the gray matter of 

 the lloor ol the fourth ventricle. Between the ventral and dorsal cochlear 

 nuclei are connecting strands of nuckuir material as well as the root fibers of 

 the cochlear ner\e and secondary libers of the cochlear tract. 



The Colliculi 



In reconstruction, these masses of gray matter are about equal in size 

 and extent. They appear as rounded elevations on the tectum of the midbrain, 

 occupying the entire width of the dorsal aspect of the axis. They are contin- 

 uous laterally with the dorsal extension of the reticular formation of the 

 mesencephalon. Mesially and dorsally they are continuous across the midline 

 with each other by means of the dorsal gray matter which serves as a matrix 

 for the superior and inferior collicular commissures. The colliculi are sepa- 

 rated from the central gray matter by these collicular commissures and by the 

 peripheral fiber condensation which is disposed as a fringe along the line of 

 contact between the central gray matter and the reticular formation. The 

 inferior colliculus is sharply separated from the large superior colliculus 

 by a narrow, finger-like process sent out by the mesencephalic reticular 

 formation, while the superior colliculus merges insensibly into the subpineal 

 region of the epithalamus. The surface of the mesencephalic reticular forma- 

 tion is traversed in this region by the passage of the two brachia connecting 

 the colliculi with the geniculate bodies. 



The Substantia Nigra 



As reconstructed, this mass of gray matter appears as a gradual trans- 

 formation in the deep layer of the pontile nuclear mass, assuming its charac- 

 teristic coloration and form at the junction of the isthmus and midbrain. It 



