THE FOREBRAIN OF THE ALLIGATOR 383 
a new type. Such a new type is introduced into the primordial 
pyriform lobe by the alveus, which carries the association fibers 
from the other developing cortical areas, particularly from the 
hippocampus. These impulses brought by the alveus are the 
resultants of a relatively high type of progressively advancing 
integration and give the physiological conditions which the 
writer has conceived of as being important in the development. 
Attention has already been called to the presence of a large 
basal somatic area in the dorso-lateral region of the forebrain in 
at least some of the reptiles. This region has been named the 
dorso-lateral area (figs. 2, 7 to 10, 12, 16 to 19, 44 to 46, DI.A., 
in this paper.- A similar if not entirely homologous area has 
been termed the dorsal ventricular ridge by Johnston (15) who 
in a recent paper (’16) has given an account of its embryological 
development. He finds that the dorsal portion of the embryonic 
brain in the turtle first gives rise by a process of cell proliferation 
to the general pallial cortex which then occupies a more super- 
ficial position. By a secondary proliferation from cells of the 
dorsal area, if the writer has understood Johnston (716) correctly, 
the dorsal ventricular ridge is formed. ‘The lateral portions are 
in relationship with the general pallial cortex and have the ap- 
pearance of being an infolding of that area in adult material. 
In the adult turtle, the dorsal ventricular ridge extends to the 
caudal end of the hemisphere, showing throughout its extent this 
relationship with the general pallium. In the alligator the ridge 
of cells (termed here primordial general cortex) is found only in 
the anterior end of the hemisphere where it has practically the 
same relationships as in the turtle. Farther caudad the dorso- 
lateral area, of which the general cortex is a differentiation, is cut 
off from the latter region by the outward and downward growth 
of the ventricle. The dorsal and dorso-medial portions of this 
dorso-lateral area, however, receive somatic fibers throughout 
practically their whole extent as far as the caudal end of the area. 
Association fibers from the hippocampus and the pyriform lobe 
distribute not only to the general cortex but also to the primor- 
dial general cortex in the anterior end of the dorso-lateral area. 
These superficial tangential association fibers have probably been 
