The brain of Acipenser. 195 
The latter bundles may correspond to my bundle y (page 99). 
The tractus tegmento-cerebellaris, I have shown (page 115), is not 
a crossed tract in Acipenser. The tracts from the ‘tween brain 
doubtless correspond to my tractus lobo-cerebellaris (page 134), the 
coarse fibres being the crossed tract, the fine fibres the uncrossed. 
I have explained elsewhere (page 218) that EDINGER failed to re- 
cognize this tract in the decussations behind the chiasma. 
HALLER (98) describes the Bindearm in the trout as made up 
of crossed and uncrossed fibres. The uncrossed fibres form two tracts, 
the upper and lower anterior Bindearme. The fibres of the upper arise 
in the cerebellum (from PURKINJE cells probably) and break up in the 
nucleus opticus lateralis. This is in all probability EDINGER’s tractus 
diencephalo-cerebellaris, and corresponds to the crossed lobo-cerebel- 
laris of Acipenser. It certainly does not arise in the cerebellum, as 
HALLER describes. The lower anterior tract runs from the cerebellum 
to the lobus inferior. This is no doubt the direct tractus lobo-cere- 
bellaris corresponding to the caudal part of the tractus diencephalo- 
cerebellaris of EDINGER, which does not arise in the cerebellum, 
but ends there. The crossed fibres are diffuse and are lost after 
crossing in the ansulate commissure. These probably make con- 
nections with the commissural cells of the base of the brain. A small 
bundle of crossed fibres runs to the thalamus. 
B. Mid Brain. 
a) Tectum opticum. 
The tectum was first studied in fishes by the GoLGI method by 
Fusari (87). Following him P. Ramon (90), BURCKHARDT (92), 
VAN GEHUCHTEN (94), NEUMAYER (95), SAUERBECK (96), MIRTO 
(95 and 96) and F. Mayer (97), applied the same method to fishes. 
The optic lobes have been exhaustively studied in Amphibia and 
Reptiles by P. Ramon (94), and in birds by S. Ramon y CAJAL 
(90b and ’91), by Van GEHUCHTEN (92) and by KÖLLIKER (96, 
p. 413—422). In Mammals incomplete investigations have been made 
by TARTUFERI (85), P. Ramon (90) and KÖLLIKER (96, p. 423—427). 
Fusarı studied the tectum of several Teleosts by the GoLGI 
method. He describes seven layers as follows, from within outward: 
1) Layer of ependyma, neuroglia, and blood vessels. 
2) Granular layer, containing besides granule cells which he can 
not interpret, spindle-shaped neuroglia cells whose processes rise to 
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