No. 1.] AMPHIBIAN BRAIN STUDIES. 79 
The Motor Tracts. As the sections extend inwards 
the mass of fibres from the medulla does not ascend, but passes 
forwards directly into the basal portion of the prosencephalon 
as the basal prosencephalic tract (basal fore-brain bundle, 
Edinger). This is best followed in the Uvodela, but is also 
readily followed in successive sections in the Anwra, Figs. 28, 29. 
Upon reaching the corpus striatum, some of the fibres of this 
tract enter this body, as described recently by Edinger (Fig. 28), 
while others pass directly into the inferior portion of the mantle 
of the hemispheres; a third portion seems to terminate imme- 
diately below the anterior commissure: but in horizontal sec- 
tions it is seen to pass to the other side.! 
The tract thus consists of three parts: a, a direct bundle 
from the hemispheres; 4, a bundle from the corpus striatum ; 
c, a decussating bundle from the hemispheres. Two of these 
divisions were incidentally described and figured in my paper 
upon the Corpus Callosum (loc. cit., Taf. XIV., Fig. 8, pm, p/). 
THE SECONDARY ENCEPHALIC TRACTS. 
Under this head may be considered the tracts which, so far 
as observed, have no direct connection with the spinal cord or 
medulla. 
Meynert’s Bundle. This is a conspicuous tract in the 
brains of all the Amphibia, 7d. It arises, in the usual manner, 
from the ganglia habenulz and descends beneath the superior 
commissure as a compact bundle of darkly stained fibres, to the 
ganglion interpedunculare. I have followed it slightly beyond 
this point in Raza, Fig. 29, but not into the medulla, as Ahlborn 
has succeeded in doing, in Petromyzon. 
The Infundibular Tract. From the infundibular lobes 
this large tract of fibres ascends, z¢, beneath the basal prosence- 
phalic tract, towards the hemispheres. Koppen has described it 
as entering the thalami. It has this appearance in Rana, but not 
in the Uvodela, where it appears to pass directly forwards and 
not upwards. 
The Posterior Commissure. The relations of this com- 
missure are threefold ; first, to the oculo-motor nucleus and prob- 
ably to the main sensory tract; second, to the pale ganglion 
1 This decussation is described by many authors as a portion of the anterior 
commissure, but in my opinion should be considered as entirely distinct, 
