THE FOREBRAIN OF THE ALLIGATOR 357 
lobe cortex itself arose as a differentiation of the neurones of the 
nucleus of the lateral olfactory tract (see Johnston 715 and the 
general discussion at the end of this paper). 
Medialward the pyriform lobe cortex is bounded by the dorso- 
lateral area and by the anterior part of the nucleus of the lateral 
olfactory tract. ‘This anterior division bears about the same rela- 
tion to the pyriform lobe cortex that the primordial hippocampus 
bears to the hippocampal cortex proper, i.e., it consists of cells 
which have practically the same type of connections as do the 
cells of the pyriform lobe cortex. It represents the general 
area from which the specialized pyriform lobe cortex has de- 
veloped. In this paper it has been considered as the anterior 
part of the complex of the nucleus of the lateral olfactory tract, 
but it might equally as well be termed primordial pyriform lobe 
cortex or the small celled portion of the pyriform lobe complex, 
as Johnston (15) has called it in turtles. (For a further descrip- 
tion of this anterior division of the nucleus of the lateral olfac- 
tory tract see the description of that nucleus). 
The writer has not been able to identify the suleus endo- 
rhinalis and the sulcus rhinalis is slight but does show in some 
preparations. The cell type illustrated in figure 39 is found in 
the anterior end of the pyriform lobe. It resembles the cells 
found in the secondary olfactory centers, which is not surpris- 
ing since the anterior end of the pyriform lobe cortex itself prob- 
ably serves to a considerable degree as such a secondary center. 
The Golgi material available for study does not show the cell 
types found in the more posterior part of this cortex. 
General cortex (figs. 4 to 10, 12,16to19). As has been stated, 
the cortex of the pyriform lobe and the hippocampal cortex are 
separated from each other by the general cortex except at the 
anterior end of the brain in the region of the olfactory lobe. 
In many reptiles this cortex forms a definite lamina separated 
from the other cortical areas by distinct limiting zones but in 
the alligator, at least in the material studied, no such sharp 
limiting zones are visible. Medialward as in the turtle, it grades 
over into the thicker dorso-medial part of the hippocampal cortex 
(Johnston’s subiculum, 715). Lateralward it is continuous with 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 27, NO. 3 
