OLFACTORY CENTERS IN TELEOSTS 193 
In the rostral part of the commissure bed is found the group 
of cellsin which terminate the fibersof the nervus terminalis. The 
pars intermedia of the corpus precommissurale consists of a 
narrow column of cells, fairly closely packed and forming a dis- 
tinct band across the ventral portion of the posterior pole of the 
hemisphere (figs. 66, 67, 68, 70). Its morphological relationships 
are obscure. 
In Golgi preparations of different parts of the precommissural 
body some of the cellular relations are brought out more fully. 
In the nucleus medianus the cells are fairly large, fusiform, pyra- 
midal or ellipsoid in shape, with almost all of their processes com- 
ing from the ends of the perikaryon as shown in figs. 28 to 31. 
A large proportion of these cells give rise to the fibers of the 
tractus olfactorius ascendens. The neurites are very delicate, 
possessing granular enlargements along their course. Smaller 
cells with a number of short, root-like dendrites and a single long 
neurite extending into the palaeostriatum, are not uncommon 
(fig. 43). Several varieties of small cells, apparently functioning 
as association cells, are found also in the nucleus medianus; 
these are chiefly stellate, or irregularly rounded (figs. 41, 42). 
In the pars supracommissuralis the cells are smaller; also rather 
more of the association cells of the type shown in figs. 41, 42 are 
found. Cells of type shown in fig. 48, sending fibers to the palaeo- 
striatum, are more common than in the nucleus medianus. Many 
of the cells of this nucleus send their neurites into the tractus 
olfacto-thalamicus medialis. Such a cell is shown in fig. 40. Small 
stellate and small pyramidal cells are rather more common than 
the type illustrated. 
(b) Primordium hippocampi. Dorsad of the sulcus limitans 
telencephali, appearing with especial distinctness rostrally, lies 
the primordium hippocampi, or nucleus olfactorius dorsalis. 
Between it and the corpus precommissurale may be seen a slight 
clear area, devoid of cells. The cells of the primordium hippo- 
camp1 are rostrally slightly smaller than those of the nucleus medi- 
anus, while dorsal to the pars supracommissuralis they are very 
similar to those of the latter nucleus (fig. 46). Many of them 
resemble the dorsal cells of the nucleus olfactorius lateralis (figs. 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 22, NO. 3 
