THE FOREBRAIN OF THE ALLIGATOR 345 
ble with the corpus striatum which Johnston has described in 
turtles. If that author has been correctly interpretated, the 
ventro-lateral small celled nucleus of this description is nucleus 
caudatus, while the ventro-lateral large celled nucleus. is the 
nucleus lentiformis of turtles. The writer has avoided the 
specific terms employed by Johnston because she does not have 
sufficient knowledge of the development of the striatum through- 
out the vertebrate series to be certain of the homologies. 
Ventro-lateral small celled area (Johnston’s nucleus cauda- 
tus). This nucleus (figs 7 to 9) begins a short distance behind 
the olfactory crus and, increasing in size, extends backward to 
the level of the anterior nucleus of the thalamus with which 
its posterio-medial portion lies in close relation. Posteriorly 
its ventral and lateral portions lie in close relation with the 
posterior part of the nucleus of the lateral olfactory tract. An- 
teriorly it cannot be sharply delimited from the nucleus ol- 
factorius anterior. Johnston (715) in turtles, where the rela- 
tionships of the caudate nucleus are practically the same as the 
relationships of this area in the alligator, has considered the nu- 
cleus olfactorius anterior and some associated gray as giving 
rise to the head of the caudate nucleus in mammals. The great 
increase in the neopallial area in higher forms is accompanied 
by an increase in the number of fibers (internal capsule fibers) 
distributing to that cortical area. These fibers are imbedded 
in the caudate nucleus and more posteriorly are ventral to it 
and so push this cell mass dorsalward and caudalward as they 
increase in number during phylogeny. The upward, backward 
and downward growth of the general cortex and the downward 
growth of the pyriform lobe have produced the typical curve of 
the caudate nucleus of higher forms. 
The ventro-lateral small celled area is continuous around 
the ventral border of the ventricle and onto its medial surface and 
this continuation represents the nucleus accumbens of higher 
forms. This apparently belongs to the striatum complex, al- 
though Johnston (’13, p. 421) has joined it to the nucleus later- 
alis septi of previous authors under the name of nucleus parol- 
factorius lateralis (see the discussion of the parolfactory nuclei). 
