The brain of Acipenser. 14% 
bear little round knobs at their ends (Phot. 59). The neurite usu- 
ally arises from the base of the large dendrite or from the basal 
part of one of its branches, occasionally from the cell body. It is 
at first a slender smooth fibre which rises in a straight course to- 
ward the periphery. Near the surface of the lobe the fibre turns 
at nearly a right angle (Phot. 69) and runs near the surface to join 
one of the tracts to the hind brain. At the point of bending, or 
before, the neurite rapidly thickens until in some cases it becomes 
more than twice as thick as in the first part of its course (Phots. 65, 69). 
Usually one or two, sometimes several, collaterals are given off from 
both the vertical and horizontal parts of the fibre (Phots. 65, 69, 70), 
In the caudal part of the lobi the neurites take a dorso-caudal course 
and form a tract which runs through the lateral wall of the mid 
brain to the cerebellum and medulla, the tractus lobo-cerebellaris et 
bulbaris rectus (page 154). In the middle part of the lobi many 
fibres take this course while others go with those from the cephalic 
portion to form part of the postoptic decussation and run to the 
same destination on the opposite side, tractus lobo-cerebellaris et 
bulbaris cruciatus. A description of these tracts is given in the 
succeeding section. 
The fibres entering the lobi come in part from the fore brain, 
tractus strio-thalamici. I shall leave the description of the course 
of these tracts until I come to treat of the fore brain (page 144), 
only noting here that the fibres are distributed to all parts of the 
lobi and end in relation with the dendrites of the cells described 
above. In addition to these, a large tract comes down from the 
tectum and in part ends in the lobe of the same side, in part 
crosses in the ansulate commissure and postopic decussation to 
end on the opposite side, tractus tecto-lobaris rectus et cruciatus 
(page 127). 
2. Corpus geniculatum. 
Just behind the optic chiasma, at the junction of the lobi in- 
feriores with the thalamus is a thickening or ridge extending across 
the middle line. The internal structure of this ridge is extremely 
difficult to make out. The cells have not such a regular arrangement 
as in the inferior lobes. They are fusiform or stellate, situated near 
the cavity or removed from it, and their dendrites are intricately 
curved and intertwined. The cell bodies are about the same size as 
those of the inferior lobes. The complication due to the irregularity 
