158 J. B. JOHNSTON, 
2nd root: larger, mostly coarse-fibred, motor. These arise in 
the same position as the Ist root in Pleuronectes. 
3rd root: large, dorsal, arising “aus dem Wulste, der der Me- 
dulla oblongata oben aufgesetzt ist, also aus dem Corpus restiforme”, 
non-motor, coarse-fibred. 
4th root: largest, of two bundles, non motor, mostly coarse- 
fibred. 
5th root: small, arises immediatly in front of VIII, exclusively 
coarse-fibred, motor. 
There can be no doubt that roots 1 and 2 in Acipenser are to- 
gether equal to root 1 in Pleuronectes, that root 3 in Acipenser is 
equal to roots 2 and 3 in Pleuronectes and that roots 4 and 5 cor- 
respond in the two fishes. While he does not give the position of 
root 4 in Acipenser, his remark that the predominance of coarse 
fibres is a peculiarity in Acipenser leaves no doubt as to its identity, 
especially as the dorsal VII could not otherwise be accounted for. 
The condition of roots 1 and 2 seems to be the same in Acipenser 
sturio (STANNIUS), A. ruthenus (GORONOWITSCH), and A rubicundus 
(present paper), the sensory and motor fibres being wholly separated 
into distinct roots. The question of the third root offers some 
difficulty. From Srannius’ description of its origin in Acipenser, 
“aus dem Wulste, der der Medulla oblongata oben aufgesetzt ist, 
also aus dem Corpus restiforme”, it seems to me that this root must 
come from the lobus lineae lateralis (Lobus trigemini of GORONO- 
WITSCH). In Acipenser rubicundus and ruthenus this root is accom- 
panied by another arising a short distance ventral from it, immediately 
ventral to the cerebellar crest, from the tuberculum acusticum (Lobus 
posterior medullae oblongatae of Stannıus). It is easily seen from 
my figures and those of GORONOWITSCH that these roots are so 
distinct in both species investigated by us that it would have been 
impossible for STANNIUS to have overlooked one of them, if con- 
ditions had been the same in A. sturio. It therefore seems prob- 
able that the dorsal root which in Pleuronectes arises in two parts 
from the “Lobus posterior” (tuberculum acusticum), arises in A. sturio 
as a single root from the ridge overlying the ,,Lobus posterior”, 
namely the lobus lineae lateralis. In A. ruthenus and rubicundus, 
then, we may have a condition intermediate between A. sturio and 
the Teleosts (Pleuronectes) in which the root is divided, one part 
still arising from the lobus lineae lateralis, the other from the tu- 
berculum acusticum. 
