OLFACTORY CENTERS IN TELEOSTS 187 
solid base of the crus at its caudal end as shown in fig. 23, gradu- 
ally decreasing in extent rostrad (fig. 22) until it forms only a 
roof for the trough-like cavity below. This cavity is morpho- 
logically a part of the ventricle of the hemispheres, extending, even 
a short distance into each bulb, as is the case with most verte- 
brates (Wiedersheim, ’02). 
Internal to the layer of olfactory nerve fibers occurs the for- 
matio bulbaris, formed chiefly by the glomeruli. The glomeruli 
are of the usual type, consisting of the terminal end-brush of 
olfactory nerve fibers, mingled with the dendrites of mitral cells, 
chiefly. The central and mesal portion of the bulb is made up of 
a mass of cells, the nucleus olfactorius anterior, the lobus olfac- 
torius anterior of Goldstein. 
According to Golgi preparations, neurones of several differ- 
ent types are found in the olfactory bulb. The most conspicu- 
ous are the large cells with short, thick, many branched dendrites, 
the mitral cells (figs. 8 to 12). These are irregular in form and 
are situated largely in the peripheral portion of the bulb, with 
their long axes approximately parallel with the surface as figured 
by Johnston, Catois, ete. The mitral cells are very irregular in 
form; pyramidal, stellate and goblet shapes being the most nu- 
merous. The dendrites of these cells, as already mentioned, break 
up in the glomeruli and there come into relation with the terminals 
of the olfactory nerve fibers. ‘Their neurites form the majority 
of the centripetal fibers of the tractus olfactorius lateralis and 
tractus olfactorius medialis. A dendrite of a mitral cell will 
often enter, also, into relation with one of the cells of the nucleus 
olfactorius anterior, usually a fusiform or stellate cell. The 
smaller cells of the bulb are more nearly central in position and 
make up most of the nucleus olfactorius anterior. Fusiform and 
stellate cells are the most numerous of these, with occasionally a 
pyramidal or goblet-shaped cell (figs. 13 to 20). The stellate 
cells, particularly of the types shown in figs. 14 and 17, are the 
most common, and are situated near’the center of the bulb, with 
their many processes extending fan shaped toward the periphery, 
where many of them enter glomeruli (Johnston, ’98, fig. 1). 
Other processes of these cells enter into relation with other cells 
