Dinoflagellates are small protists and usually
unicellular. Most of these organisms have two unequal flagella, one extending
longitudinally from the posterior end of the cell, the other encircling the
central part of the cell. Some dinoflagellates extend trichocysts like the
paramecium; others have nematocysts, stinging cells common in the coelenterates.
Some species --Noctiluca, for example -- are bioluminescent, giving off light
like a firefly.
