Dinoflagellates are unicellular algae that are ubiquitously abundant in aquatic environments.

Red-snow algae are red-pigmented unicellular algae that appear seasonally on the surface of thawing snow worldwide.

C. paludica fed mainly on detritus and invertebrates while Cobitis calderoni fed on invertebrates and unicellular algae.

Unicellular algae found in aquatic and damp terrestrial habitats.

Probably the Noctiluca is not rivalled in this respect even by miscroscopic unicellular algæ which compose the "red snow."

In this bladder, as well as in several others, there were some unicellular Algae, and one multicellular Alga, which no doubt had lived as intruders.