The brain of Acipenser. 203 
Tractus bulbo-tectalis. — Mayser (81) describes a 
“Lemniscus REIL’, an “untere Pyramide”, and an “intermediäres 
System” between the two, which doubtless correspond to part or all 
of the tractus bulbo-tectalis and tecto-bulbaris. 
EDINGER (’96b) describes two tractus acustico-tectales, one through 
the lower olive via the fillet to the tectum, the other crossing beneath 
and through the fasciculus longitudinalis posterior. The latter 
(dorsal) is strongly developed in the lower Vertebrates, while the 
former (ventral) is well developed only in the higher Vertebrates. 
The dorsal tract corresponds to the tractus bulbo-tectalis in Aci- 
penser (page 127). It has been described also by C. J. HERRICK 
(99, p. 206). It is possible that the ventral tract may be represented 
in Acipenser by the superficial arcuate fibres from the acusticum 
which I have suggested above (page 80) were external arcuate fibres. 
Tractus thalamo-tectalis. — This tract has been de- 
scribed by EDINGER (99) as coming from the nucleus rotundus 
thalami in Reptiles. Although he has not described this nucleus 
and bundle in detail in his special paper on the ‘tween brain of 
fishes and Amphibia (92), in the Vorlesungen (96b) he describes 
them and says that the nucleus “ist auch bei den Fischen ein 
michtiges Ganglion”, and that “das Aussehen dieses Kernes und 
seine Verbindungen sind überaus charakteristisch und überall un- 
verändert”. In Acipenser the condition is more primitive than in 
the forms studied by EDINGER in that the nucleus is not defined 
and the tract, if present at all, is diffuse and difficult to follow. 
The Mantelbiindel are described by EDINGER (99) as coming 
from the lateral part of the cortex, crossing in the decussatio post- 
optica, and going to the dorso-caudal part of the mid brain. In 
the Torpedo, Triton, and Salamandra he says expressly that the 
bundle runs to the tectum. 
The tracts in the dorsal part of the thalamus, part of which 
may enter the tectum, will be treated below (page 213). 
2. Centrifugal Tracts. 
These are the tractus tecto-bulbaris and tractus tecto-lobaris, 
both of which are in part crossed tracts (page 125, 127), the tractus 
tecto cerebellaris, and perhaps smaller tracts to the thalamus and 
fore brain. Mayser (81) describes, in addition to the bulbar tracts 
above mentioned, tracts to the lobus inferior, part of which cross 
