The brain of Acipenser. 237 
rites to the ganglia habenulae through the commissura superior 
(F. MAYER, 97, p. 651). Cells of this description must belong to 
the area olfactoria. 
It is unnecessary for me to review STUDNIGKA’s papers, except 
to refer to one (98) in which he cites the facts in my preliminary 
paper (98a) as supporting his view. He considers that the existence 
of a group of cells on the lateral surface of the striatum which is 
probably in connection with the olfactory bulb and with the ganglia 
habenulae, supports the hypothesis that the cortex is derived from 
the striatum. STUDNICKA has apparently been misled here by the 
use of the word “cortex”. The connections on which he lays stress 
are only the usual connections of cells of the area olfactoria. As 
will appear below, the basis for my use of the word “cortex” was 
the commissural character of the cells, and I have indicated that I 
was in error in applying the name “tractus cortico-habenularis” to 
the fibres to the ganglion habenulae. In a footnote STUDNICKA 
states that my description of nerve cells in the membraneous roof 
is X9 evidence of the homology of that membrane. The fuller de- 
scription in this paper and the following comment will, I think, 
show that these cells are not to be passed over so lightly. 
It is difficult or impossible to compare the cells in Acipenser, 
to which I have given the name cortex, directly with any cells 
heretofore described. The cells are in two distinct groups, one 
lying on the lateral surface of the striatum aud sending their neu- 
rites to the opposite side through the anterior commissure; the other 
lying in the membraneous roof near the junction with the olfactory 
lobes and connected by a small bundle of fibres with the area ol- 
factoria or the striatum. The neurites of the first group of cells 
seem to form the pars corticalis of the anterior commissure. This 
pars corticalis is not accurately understood in any Vertebrate. In 
Reptiles EpıngEr (96a) describes a ramus transversus corticalis of 
the anterior commissure, but it is uncertain whether it connects the 
cortex of the two sides with one another, or connects the cortex 
with the striatum or epistriatum of the opposite side. In Acipenser 
the cells in question are special cells of association between the ol- 
factory centers of the two sides, receiving the short neurites of the 
epistriatum cells and perhaps olfactory tract fibres, and sending their neu- 
rites to the epistriatum of the other side. A comparison of EDINGER’s 
figs. 76 and 100 in the 5th edition of the Vorlesungen with Phot. 3 and 
Pl. 13 of this paper will show that there has been a great increase 
