142 JOURNAL OF ENTOMOLOGY AND ZOOLOGY 
species, and all that could be seen in the sections were occa- 
sional very minute ganglia. The gastro-esophageal ganglia 
which are described as occurring on the anterior border of the 
bueeal ganglia in typical Doridide, are apparently completely 
fused with the buecal, which are regularly ovoid in shape and 
show no protuberances or other trace of the gastro-csophageal 
ganglia, excepting the single nerve. 
The olfactory ganglia, which are about 150 microns in their 
longest diameter, are closely attached to the upper, anterior 
border of the cerebral. They give off a single pair of large 
nerves, the olfactory. These go forwards for some distance 
and pass through the muscles of the body wall, but instead of 
entering the rhinophores directly, go downward and then bend 
sharply, thus making an S-shaped bend in their course. This 
is undoubtedly because of the retractility of the rhinophores, 
all of the observations being of necessity made on retracted 
rhinophores, as the animal withdraws them upon the slightest 
disturbance. Within the trunk of the rhinophore in the con- 
tracted condition, the nerve has a knotted and twisted appear- 
ance. 
The cerebro-pleural ganglia are by far the largest, measur- 
ing nearly .6 mm. lengthwise. They are roughly rectangular 
in shape, and, as has been stated, appear from the upper side 
as a single pair of ganglia, but on the lower side are divided 
transversely into two lobes. In section also they show a trans- 
verse division into two centers. They are connected dorsally 
by a large, very short, cerebro-pleural commissure, which con- 
tains fibres anteriorly from the cerebral and posteriorly from 
the pleural portions of the ganglia. Ventrally they are joined 
by the visceral commissure, which bears the visceral ganglia 
and has its origin on the under side of the posterior part of 
the pleural ganglia. Besides the nerves of the rhinophores, 
eyes, and otocysts, the cerebro-pleural ganglia give off eight 
pairs of nerves. Five of these, which are given off close to- 
gether on the anterior lateral border, may be said to arise 
from the cerebral ganglion. The nerves numbered 2, 3, 5, 6 in 
the figure all give branches to the muscles around the mouth, 
