The nervous system is fairly well developed; and
the two almost confluent cerebral ganglia are situated very near to
the anterior end of the body.
Senses.--Worms are destitute of eyes, and at first I thought that
they were quite insensible to light; for those kept in confinement
were repeatedly observed by the aid of a candle, and others out of
doors by the aid of a lantern, yet they were rarely alarmed,
although extremely timid animals. Other persons have found no
difficulty in observing worms at night by the same means. {14}
Hoffmeister, however, states {15} that worms, with the exception of
a few individuals, are extremely sensitive to light; but he admits
that in most cases a certain time is requisite for its action.
These statements led me to watch on many successive nights worms
kept in pots, which were protected from currents of air by means of
glass plates. The pots were approached very gently, in order that
no vibration of the floor should be caused. When under these
circumstances worms were illuminated by a bull's-eye lantern having
slides of dark red and blue glass, which intercepted so much light
that they could be seen only with some difficulty, they were not at
all affected by this amount of light, however long they were
exposed to it. The light, as far as I could judge, was brighter
than that from the full moon.
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