e
velocity. Its upper portion is slowly twisted through the opening in the
apex of the parent wall, the granular contents of the lower end flowing
into the extruded portion in a manner reminding one of the flow of
protoplasm in a living amoeba. The old cell wall seems to offer
considerable resistance to the escape of the gonidium, for the latter,
which displays remarkable elasticity, is pinched nearly in two while
forcing its way through, assuming an hour glass shape when about half out.
The rapid rotation of the spore continues during the process of emerging,
and after about a minute it has fully freed itself (Fig 1, a). It
immediately assumes the form of an ellipse or oval, and darts off with
great speed, revolving on its major axis as it does so. Its contents are
nearly all massed in the posterior half, the comparatively clear portion
invariably pointing in advance. When it meets an obstacle, it partially
flattens itself against it, then turns aside and spins off in a new
direction. This erratic motion is continued for usually seven or eight
minutes. The longest duration I have yet observed was a little over nine
and one-half minutes. Hassall records a case where it continued for
nineteen minutes. The time, however, varies greatly, as in some cases the
motion ceases almost as soon as the spore is liberated, while in open
water, unretarded by the cover glass or other obstacles, its movements have
been seen to continue for over two hours.

The motile force is imparted to the gonidium by dense rows of waving cilia
with which it is completely surrounded. Owing to their rapid vibration, it
is almost impossible to distinguish them while the spore is in active
motion, but their effect is very plainly seen on adding colored pigment
particles to the water. By subjecting the cilia to the action of iodine,
their motion is arrested, they are stained brown, and become very plainly
visible.

After the gonidium comes gradually to a rest its cilia soon disappear, it
becomes perfectly globular in shape, the inclosed granules distribute
themselves evenly throughout its interior, and after a few hours it
germinates by throwing out one, two, or sometimes three tubular
prolongations, which become precisely like the parent filament (Fig 2).

Eminent English authorities have advanced the theory that the ciliated
gonidium of _Vaucheria_ is in reality a densely crowded aggregation of
biciliated zoospores, similar to those found in many oth