The brain of Acipenser. 81 
branches. The smaller branch enters the spinal V tract while the 
larger goes on into the acusticum. Some relatively fine fibres seem 
to enter the spinal V tract without branching. The total number 
of fibres entering this tract is small. I have traced a few fibres to 
terminal branches around certain cells lying near the ventricle in 
the plane of the root, which I take to be the same as the Acusticus- 
zellen of GORONOWITSCH. These cells measure 8—24 by 28—144 u. 
They send their neurites ventro-cephalad to the other side of the 
medulla through the caudal part of the ansulate commissure. Some 
of the acusticus fibres form a small compact bundle which takes an 
ascending course on the internal surface of the acusticum and is 
closely invested by small cells whose dendrites wrap around the 
bundle and penetrate between its fibres. The bundle grows smaller 
owing to the fibres breaking up in relation with these cells. Al 
the fibres thus far mentioned represent much the smaller part of 
the VIII root. The destination of the remaining greater number 
of fibres is difficult to determine owing to their becoming in- 
distinguishably mingled with the lateral line fibres. The larger part, 
however, take an ascending course and enter the cerebellum, as 
will be described below (page 97). A considerable number of VIII 
fibres seem to take a descending course. Of these part join the 
spinal VIII tract described above and the remainder end in the 
acusticum. The same correction regarding arcuate sensory fibres is 
to be made here as in the case of the trigeminus and lateral line 
nerves. 
Lobus lineae lateralis (Lobus trigemini of Goro- 
NOWITSCH). — For the sake of simplicity and clearness I have thus 
far not mentioned this structure in connection with the description 
of the acusticum. It is a prominent ridge overlying the cerebellar 
crest and extending from about the lateral line X nerve to a point 
a little caudal to the V nerve. It was called by GORONOWITSCH 
the “Lobus trigemini” and the nerve root arising from it he called 
the dorsal root of the second trigeminus (7.IId). The nerve 
elements in this body correspond in every particular to those in the 
acusticum as described above, and in my previous communication I 
have described it as a part of the tuberculum acusticum (98 b, p. 586), 
and suggested the name lobus lineae lateralis. In the ventral 
portion of the lobus, bordering on the cerebellar crest, are found 
true PURKINJE cells. These measure 6—32 by 40—256 u, and have 
the same characteristics as those in the acusticum. There are also 
Zool. Jahrb. XV. Abth, f. Morph, 6 
