172 J. B. JOHNSTON, 
scending fibres of V “apparently correspond with those to the chief 
sensory nucleus of Menidia and other forms. There is no evidence 
that they terminate in the tuberculum acusticum proper” (p. 204). 
I think my description makes it clear that the tract in question does 
end in what I consider to be the tuberculum acusticum. The dif- 
ferentiation of the common nucleus of the VIII, lateral line, and 
V nerves into tuberculum acusticum proper and other distinct nuclei, 
however far it may have gone in Teleosts, has not taken place in 
Acipenser (cf. succeeding paragraphs). 
HERRICK’s reference to descending fibres from the cerebellum 
to the V described by GORONOWITSCH and myself is an oversight, 
since no such fibres have been described. Neither my previous de- 
scription (98b, p. 586) nor that in the present paper (page 76) 
makes mention of such fibres. The description by GORONOWITSCH 
(89, p. 513) is as follows: “Die feinfaserige dorsale Wurzel des 
Trigeminus I bekommt ihre Fasern aus einem aufsteigenden und 
absteigenden System. Wie bei den vorigen Nerven konnte ich den 
Ursprung des aufsteigenden Systems nicht ermitteln. Ein Theil der 
Fasern des absteigenden Systems läuft eine Strecke weit proximal, 
wendet sich fast senkrecht dorsalwärts zu dem seitlichen Theile des 
Cerebellum, wo er bald verschwindet. Ein anderer Theil ist bis zum 
Mittelhirn zu verfolgen”, which (he thinks) probably corresponds to 
MAYSER’s descending V root. When it is remembered that Goro- 
NOWITSCH uses the terms ascending and descending in the 
opposite sense to that which HERRICK and I give them it is evident 
that GORONOWITSCH’S descending tract from the cerebellum is 
exactly the same as my ascending tract which ends in the nucleus 
“lying under the cerebellum”, as HERRICK describes it. GORO- 
NOWITSCH’s description, as far as it goes, agrees with mine, except 
that I do not find any mid brain root of the V. GoRONOWITSCH 
has apparently become confused among the great number of tracts 
intermingled at the junction of the mid brain and cerebellum, and 
has probably traced one of the parts of the tractus tecto-cerebellaris, 
under the impression that it was the continuation of part of the 
V fibres. This is a mistake easily made in trying to trace these 
tracts in haematoxylin preparations. 
Internal and external arcuate fibres. — HERRICK 
describes (99, p. 206) secondary fibres from the acusticum crossing 
to the opposite side and forming a tractus bulbo-tectalis, which 
agrees with my description (page 79). It seems to me that these 
