The animals move with the narrow apex forwards, by the aid of their vibratory ciliae, and generally by rapid starts.

They are exceedingly minute, and quite invisible to the naked eye, only covering a space equal to the square of the thousandth of an inch.

Their numbers were infinite; for the smallest drop of water which I could remove contained very many.

In one day we passed through two spaces of water thus stained, one of which alone must have extended over several square miles.

What incalculable numbers of these microscopical animals! The colour of the water, as seen at some distance, was like that of a river which has flowed through a red clay district; but under the shade of the vessel's side it was quite as dark as chocolate.