GANGLIA AND NERVES OF SQUALUS 29 
both the olfactory and terminalis nerves to be much more de- 
veloped and better isolated at 25 mm. than in my specimen of the 
same age. In fact, one would infer from his description that 
at 16 mm. the connections of the olfactory and terminalis nerves 
were more definite than in the 22 mm. embryo plotted in this 
paper. 
At the posterior end of the connecting mass in all specimens 
examined there are two strands of cells which detach them- 
selves trom the main mass and come into contact with the olfac- 
tory epithelium ai a point more ventral and posterior to the 
chief mass. These masses in none of my earlier specimens con- 
tain fibers and the strands are absent in a 30 mm. specimen. 
This connecting mass appears to be, on first examination, in 
a rather undifferentiated condition as indicated by the small 
proportion of fibers, and the very large number of cells. An- 
other interpretation however is possible, namely, that the large 
mass of cells represents the beginning of the close fusion be- 
tween. the olfactory capsule and olfactory bulb characteristic of 
Squalus in addition to early sheath cells of the n. terminalis and 
n. olfactorius The olfactory capsule contains at all points ex- 
cept the anterior border a well defined basement membrane. 
At the anterior border this membrane is lacking and the cells 
of the capsule mingle with those of the mass of cells connecting 
the capsule with the brain wall. Younger embryos, in which the 
connecting mass is not so large, present the appearance of a 
migration of cells from the capsule to what I have designated the 
connecting mass. However, my series of embryos is not suffi- 
ciently large to determine definitely the origin and fate of this 
mass of cells. It seems from a comparison with the conditions 
in Amia, Ameiurus, and Lepidosteus (Brookover, 1908, 1910, 
1911) entirely too large to be the ganglion of the nervus termi- 
nalis and I am inclined to interpret it as the beginning of the 
fusion of the capsule with the bulb plus early sheath cells, as 
indicated above. The connecting mass is much smaller in 
younger embryos and shows a decided increase in size in a 23 
mm. embryo as compared with the 22 mm. embryo plotted. 
