CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
753 
the molecular layer with the Purkinje cells and the fibrous layer. Anteriorly each 
torus commences by a rounded projection into the roof of the aqueduct, then passes 
dorsad along the anterior wall of the channel forming the communication between 
the ventricle and the aqueduct; and, passing forward along the floor of the anterior 
lobe, amalgamates at the anterior end of the cerebellum with the dorsal tuberosities, 
forming a mass of granular layer occupying the whole thickness of the lobe at that 
point; the two tori then pass along the whole length of the dorsal wall to the 
posterior end of the cerebellum, where an arrangement is found resembling that at 
the anterior extremity; hence the tori are to be traced into the ventral wall of the 
posterior lobe, and from there downward along the posterior wall of the channel above 
mentioned, then backward along the roof of the sinus rhomboidalis; finally, they 
turn upward, and end in a club-shaped free extremity as it appears in a longitudinal 
section. A consideration of the description just given would seem to show that, 
properly speaking, there are only two tori in the granular layer, since the dorsal and 
ventral are continuous at each end of the cerebellum. 
Transverse sections (fig. 13) show that the inferior lobe is the medium of communi¬ 
cation between the cerebellum and the medulla oblonqata through the restiform 
bodies. The junction is effected at the lateral part of this lobe. Through the con¬ 
necting link the fibres of the crura cerebelli ad medullam pass from one to the other. 
Owing to the folding of this lobe the section passes through the granular tori twice, 
giving the appearance as if there were four, two projecting into the ventricle of the 
cerebellum and two into the roof of the fourth ventricle. At the point of junction 
of this lobe with the restiform columns, the crura cerebelli part into two divisions, 
one, the external, passes upward along the outer wall of the cerebellum to the dorsal 
angle, then turning inward joins that of the other side in the mid-line, crossing through 
the bases of the two dorsal tori of the granular layer. In the central line, at the 
bottom of the fissure which divides the two tori from each other, the wall of the 
cerebellum consists only of the commissure in question, and a modified molecular 
layer, much narrower than at the other parts of the cerebellum. The internal division 
of the crura goes partly upward, and forms a commissure through the bases of the 
upper tuberosities of the inferior lobe, and partly downward to make a corresponding 
commissure through the lower tuberosities. At both the upper and lower central 
points the wall is composed only of the transverse fibres, and a small portion of the 
molecular layer. 
The inferior lobe (fig. 17) is the only part which Miklucho-Maclay allows to 
belong to the hindbrain, all the remainder of the cerebellum belonging in his view to 
the midbrain or mesencephalon. But this view is untenable, the inferior lobe is 
clearly nothing more than a fold of the cerebellum with no independent characteristic 
whatever ; it has no ventricle, nor any indication of relationship to the primitive 
vesicles of the brain, as a glance at the figures given by Balfour'" would show. 
* ‘ Development of Elasmobrancli Fishes,’ Plate xv., fig. 7a. 
5 D 
MDCCCLXXXVI. 
