348 ELIZABETH CAROLINE CROSBY 
it lies for:'the most part, medial to the pyriform lobe cortex in- 
stead of ventral to it as in turtles. Furthermore the anterior, 
dorsal end of the nucleus of the lateral olfactory tract (Johnston’s 
small celled, ventral portion of the pyriform lobe) is much larger 
in the alligator than in the turtle and this increase in size has 
probably been another important factor in bringing about the 
change in the relative positions of the two cell masses. 
The more ventral and posterior portions of the nucleus of the 
lateral olfactory tract as that nucleus has been described for 
the alligator are comparable to nearly all of the nucleus of that 
name described for the turtle (Johnston, ’15). Here again, 
however, there is one point of difference, for, while in the turtle 
the nucleus occupies the outer portion of the hemisphere in the 
posterior part of the forebrain, in the alligator the cortex of the 
pyriform lobe extends downward and occupies the outer portion 
of the ventral wall, the nucleus of the olfactory tract lying in- 
ternal to it and in close relation with it. (For a further dis- 
cussion of these relations and their significance see the account 
of the pyriform lobe.) 
To summarize, the nucleus of the lateral olfactory tract as it 
is present in the alligator is practically the equivalent of the 
nucleus of that name and the small celled ventral part of the 
pyriform lobe in turtles, except that the last named area has 
been greatly elaborated in the alligator and its more anterio- 
dorsal portion may very well have taken on an added significance 
from its intimate relation with the somatic dorso-lateral, area. 
Ventro-medial nucleus (figs. 10, 12, 18, to 21). This nucleus 
occupies the extreme ventro-medial portion of the hemisphere, 
extending throughout about the posterior half of the hemi- 
sphere. It has broad connections with the habenula by way 
of the stria medullaris and it gives rise to the great olfactory 
projection tract of Cajal. 
This quite evidently is the medial, large-celled nucleus de- 
scribed by Johnston (715) for Cistudo carolina, although the cells 
of this nucleus, in the alligator, resemble in size and in cell char- 
acteristics the cells of the nucleus of the lateral olfactory tract, 
except that they are massed somewhat more closely together. 
