284 
best shown. A gan- 
glionic enlargement 
(gl) is seen in the 
course of the median 
nerve. 
Fig. 11 shows a 
similar section of the 
brain of an older em- 
bryo 38 mm long after 
the formation of the 
lobe. On the left side 
is shown the median 
nerve (nv), the lobe 
Fig. 10. Section through the fore-brain of an Acanthias (Lob) and four nerve 
embryo 20 mm long before the formation of the olfactory bundles belonging to 
lobe. ; 
the main olfactory. 
Ber 
er 
vob 
Fig. 11. Section through the fore-brain of an Acanthias embryo 381/, mm long 
after formation of olfactory lobe. 
Figs. 12, 13 and 14 show three sections made in the horizontal 
plane through the olfactory apparatus of an embryo 72 mm long. 
In Fig. 12 the lobe (Lob) is shown attached to the brain-wall (br). 
The two chief divisions (a and b) of the main olfactory are well shown, 
and also the two clusters of glomeruli, located in the distal part of 
the lobe, with which the fila olfactoria are related. The median nerve 
(nv) which might be called the accessory olfactory is shown in cross- 
section midway between (a) and (b). 
Fig. 13, made at a lower level, shows the lobe (Lob) separated 
from the brain-wall. Nerve fibres, mainly from division (b), are seen 
passing between the folds of the olfactory membrane. Two separate 
clusters of glomeruli are evident as in the former Fig. Under the 
