The brain of Acipenser. 137 
8) Commissure of the secondary vagus nucleus. 
Divides into three in the cerebellum (cf. page 87 ff.). 
9) Tractus lobo-cerebellaris cruciatus, third bundle. 
Crosses ventral to the commissure of the secondary vagus nucleus 
and forms a medullated commissure through the body of the cere- 
bellum (cf. page 134). 
10) Tractus tecto-cerebellaris I and II. Enter dorsal 
to the tracts from the lobi inferiores (cf. page 128). 
11) Ascending trigeminus and nucleus (cf. page 77). 
f) Commissura ansulata (Fig. M). 
Most of the constituents of this so-called commissure have been 
described or mentioned in the preceding pages. I shall attempt 
here to bring into their proper relations all the bundles crossing 
in the base of the mid brain. As indicated in Fig. M, the com- 
pe De Su Len 
missure is much thicker at its cephalic border, which is more 
definitely limited than the caudal border. It is difficult to distinguish 
any caudal limit to the commissure, since one of its fundamental 
elements is present in the whole extent of the medulla and cord. 
1) Throughout the whole commissure are numerous fibres which 
arise from the commissural cells of the ventro-lateral columns. These 
constitute a common element in the commissura ansulata and the 
decussatio ventralis of the medulla and cord. The most cephalic 
