CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
749 
A layer of neuroglia surrounds this group of cells, as before mentioned, on all sides 
except posteriorly, in which with high powers only very fine granules are to be 
observed. The above described cells occur very sparingly here. 
The external portion of the lobule (fig. 1, o.l.) is formed principally by the fibres of 
the olfactory nerve. These fibres enter at the anterior end, and occupy about half the 
length of the lobe ; they do not go straight, but the bundle dividing at the apex 
forms an interlacing layer which encloses the fore part of the lobe as in a sheath, and 
envelopes small rounded masses of coarse granular neuroglia, which may be looked 
upon as representing the glomeruli in the bulbus olfactorius of Mammalia, described 
by Meynert (81). 
Larger cells are seen to occupy the inner edge of this layer of nerve-fibres, where it 
begins to pass over into the stratum of finely granular neuroglia above described ; at 
this part the neuroglia is coarser, and the cells in question occupy spaces therein in 
the same way that the small cells do in the central group. These cells (fig. 15, e.f.) 
are mostly tripolar, with sometimes one, and sometimes two broad protoplasmic 
processes, the others being fine and probably axis- cylinder prolongations. They 
measure 0'013 millim. long by O'OIO millim. broad, the nucleus measuring 0'007 
millim. by 0‘006 millim. ; some have a distinct spot-like nucleolus, which, however, 
in many specimens cannot be so easily distinguished. Besides these, other unipolar 
cells (fig. 15, c .) occur in which the protoplasm greatly preponderates, and where the 
nucleus is not much larger than that of the small cells of the central group. The 
specimen figured has a spot-like nucleolus placed nearly in the centre of the nucleus. 
In addition to the larger cells, which as before mentioned occupy the border of the 
layer of fibres, some of these fibres themselves show cell-like swellings (fig. 15, d .) in 
their course, which somewhat resemble the cells described by Meynert ( 81 ) in the 
glomeruli olfactorii of the human subject. These cell-like swellings in the course of 
the fibres are like some kinds of bipolar cells : they have large oval nuclei and con- 
spicuous nucleoli. The length of the one figured is 0 - 020 millim. and the width 
0 006 millim., the nucleus measuring 0'006 millim. by 0’004 millim. 
In the Whiting Pollack ( Merlangus Pollacliius ) the olfactory lobes are situated 
beyond the cranial cavity, close over the nasal sacs, and are connected to the cerebral 
lobes by two long commissures. Here the structure very much resembles that of those 
lobes m the Grey Mullet ( Mu.gil cephalus ), above described. In these, also, the group 
of small cells is found to be surrounded by the layer of finely granular neuroglia ; 
and outside of all comes the fibres of the olfactory nerve. 
That these lobes homologise the bulbi olfactorii of Mammalia will be seen by 
comparing a section through the olfactory lobe of the Teleostean, with a similar 
section through the bulbus olfactorius of the monkey, as described by Meynert ( 81 ). 
According to that author a section from outside inwards shows first, the olfactory nerve 
layer ; next, a stratum glomerulosum containing glomeruli olfactorii, then a stratum 
gelatinosum in which the ganglion cells are more closely aggregated internally, finally 
