128 J. B. JOHNSTON, 
sticum, and it is probably these fibres which cross in the ansulate 
commissure, so that all the secondary fibres from the acusticum 
cross to the opposite side before they reach the tectum. 
6) Tractus strio-tectalis (2) or Mantelbündel. — Accom- 
panying the tractus tecto-lobaris on its cephalic border is a small 
number of coarse fibres which come from the lateral border of 
the tectum, from the middle fibre zone. These fibres are so in- 
timately associated with those of the tractus tecto-lobaris that I at 
first considered them as a second part of that tract. But the fact 
that the fibres are coarse is against this interpretation, while their 
crossing behind the chiasma suggests that they correspond to 
EDINGER’s Mantelbündel in Selachians. It has been impossible to 
determine, in this difficult region, the further course of the fibres 
after crossing. Some of my preparations give the impression that. 
they go forward with the tractus strio-thalamicus, and I am inclined - 
to think that this is the case. Whether these fibres arise in the 
striatum and end in the tectum, or arise in the tectum and end in 
the cortex or epistriatum, I do not know. The tract is represented 
in Pl. 13 as if arising in the tectum, and is shown only as far as 
the postoptic decussation. 
7) Tractus tecto-cerebellaris I and II. — This tract is 
much smaller than those to the lobi and medulla, but is still of con- 
siderable size. It is divided into two parts, the smaller (I) consisting 
of coarse fibres, the larger (II) consisting of fine fibres. The greater 
part of the coarse-fibred bundle arises from the cephalic part of the 
tectum. I have been unable to find its cells of origin. The greater 
number of the fibres arise from the vicinity of the large-celled 
nucleus. I have traced the fibres down among these cells, but 
there are no cells impregnated when the fibres are stained. Other 
fibres join this bundle from the cephalic border of the dorsal de- 
cussation. The fibres, which are relatively coarse and are beautifully 
impregnated in many preparations, form a compact bundle which 
courses around the lateral border of the tectum in the bottom of 
the shallow groove which limits the tectum laterally. As it 
proceeds it is augmented by occasional fibres from the lateral 
part of the tectum. When the bundle reaches the point of junction 
of the tectum and cerebellum it enters the cerebellum and is distri- 
buted to the body and valvula. As the bundle enters the cerebellum 
the fibres grow distinctly larger, then divide into two nearly equal 
branches, each of which further increases in size and becomes 
