( 899 ) 
I wish here to say that the great distance between IV nucleus 
and quintus-root is not to be attributed solely to the frontal shifting 
of the former nucleus. The isthmus in the Selachian is much more 
extended than in the more compressed brain of Petromyzon *) and 
likewise more than in the Teleosts. That, however, a considerable 
frontal shifting of the trochlear-nucleus has taken place is also appa- 
rent from the facts that a great part of the nucleus now lies in 
front of its root-entrance, and that the IIL and IV nuclei overlap 
each other for a part, while in Petromyzon there was a large gap 
between them. 
Thus we find in these Selachii a strong frontal shifting of the IV 
nucleus as compared with Petromyzon. 
RIV af 
fim 
NUIT 
Fig. 3. Lophius. 
Passing on to the relation in Teleosts, I refer to Fig. 3, in which 
the topographic relations of Lophius are given. Here in the oculomotor 
nucleus a great difference is noticeable as compared with Selache 
owing to a part of the III nucleus having undergone a strongly 
ventral shifting (Figs. 3, 11, and 12). 
This ventral shifting should not surprise us, for it is known that 
the abducens nucleus in these animals also oecupies a ventral posi- 
tion. It is highly probable that here too, the strong development of 
the ventral tecto-bulbar (optic) reflex tract is the cause of this dis- 
placement which, for the decussated reflexes also, may perhaps find 
support in the fact that the place of the lowest point of the nucleus 
agrees with the ventral decussation level of the above-mentioned 
reflex-tract, which lies (as we know from pr LANae’s *) researches) 
principally before, partly on the level of the III root entrance and 
!) The compressing of tie Petromyzon-brain is also conspicuous in the fore-brain 
to which Scorr has already referred. (Journal of Morphologie Vol. 1, p. 253). 
2) Karpers. The migrations of the V, VI, and VII nuclei ete. Verhand. der Kon. 
Akad. v. Wetensch. Vol. 16, 2de Sectie. 
5) De Large. The descending tracts of the corpora quadrigemina. Folia Neuro 
biologica. Vol. Ill, p. 644. 
