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By subjecting the cilia to the action of iodine, their motion is arrested, they are stained brown, and become very plainly visible. 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 other confervoid algæ.
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.
These contents are now gradually forming themselves into the spore or "gonidium," as Carpenter calls it, in distinction from the true sexual spores, which he terms "oospores." In a less noticeable degree, this is also the case in the other parts of the circumference of the cell, and, apparently, the granular contents have secreted a separate envelope entirely distinct from the parent filament.
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. 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.
It would seem to be a reasonable inference, I think, based upon the theory above stated, that in this case the newly formed gonidium, unable to escape from its prison by reason of the abnormal strength of the cell wall, became after a while resolved into its component zoospores.
It is also to be noted as a significant fact, that the cellulose wall was intact at the apex, instead of showing the opening through which in ordinary cases the gonidium escapes.
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