Like so many coloured Protista, they frequently possess a pigmented " eye-spot " in which may be sunk a spheroidal refractive body (" lens ").
It is doubtful, however, whether the conventional distinction between plants and animals will continue to be urged; and the suggestion of Haeckel that a class Protista should be established to receive the forms exhibiting both animal and plant affinities has much I.
They enlarge and diminish, and are possibly excretory like the " contractile vacuoles " of other Protista; though it has been suggested that by their communication with the medium they subserve nutrition.
How would you define protista? Add your definition here.