The brain of Acipenser. 213 
of MEYNERT not only avoid the corpus interpedunculare to end in 
a neighboring nucleus as in Acipenser, but even give part of their 
fibres to the nucleus rotundus. If the Trapezkern of WESTPHAL 
should prove homologous with the end-nucleus in Acipenser, we 
might expect to find both this nucleus and the corpus inter- 
pedunculare present in fishes, Amphibians, and the lower Reptiles, 
and that a divergence has taken place in the descendants of the 
Reptiles such that the ganglion interpedunculare has become more 
important in the Mammals, while the other nucleus has become pre- 
dominant in the birds. The statement of KOLLIKER that in man, in 
the absence of the corpus interpedunculare, the bundles of MEYNERT 
are in a state of degeneration requires confirmation. It is possible 
that here there is a second nucleus. Until further human and com- 
parative investigations on the subject of this second nucleus are 
made the manner of ending of MEYNERT’s bundles must remain im- 
perfectly understood. Further investigations are also desirable upon 
the destination of the fine fibres which in Acipenser seem to go to 
the cerebellum. These have not been mentioned by any other author. 
I have retained the name “bundles of MEYNERT” because I believe 
that it is better to use the old name until the bundles are better 
understood. 
b) Thalamus. 
1, Dorso-cephalic Part of Thalamus. 
As appears from the description (page 112) the part of the 
thalamus lying immediately ventral to the ganglia habenulae has a 
complex structure, including three nuclei and several sets of fibres. 
Most of the structures which I have described in this region have 
not been described before. The relations of the nucleus anterior 
have been set forth by EDINGER in the Vorlesungen (96b) and in 
his last paper on the ‘tween brain (99). The nucleus to which 
EDINGER gives the name nucleus praetectalis (ll. cc.) he thinks 
probably belongs to the tectum. I have applied the same name to 
a group of cells in the same position which send their neurites into 
the tectum. I can not regard this as belonging to the tectum, but 
as EDINGER does not describe the neurites of his nucleus prae- 
tectalis it is possible that I have not found the same nucleus in 
Acipenser. Apparently this dorsal region corresponds in whole or 
in part to the nuclei medius, dorsalis, lateralis, and intermedius and 
a part of the stria medullaris in Mammals (KÖLLIKER, 96, p. 472). 
