Darwin and 'Water-Bloom'

Abstract

SOME years ago, I described the formation of red 'water-bloom' in the seas round Cape Peninsular, by myriads of the ciliate Mesodinium rubrum Lohmann¹. I had been unable to find references (in the literature available on the spot) to ciliates as a cause of this phenomenon, though 'water-bloom' caused by various other micro-organisms was well known in many localities. A reply from Prof. O. Paulsen² showed that formation of red 'water-bloom' due to Mesodinium had been seen by him at Iceland thirty years earlier. The Danish publication was out of my reach at the time, but I ought not to have missed the astoundingly accurate, detailed description of Mesodinium forming red water made by Darwin³ some fifty years earlier still, before Mesodinium had in fact been named. No one who has examined swarming Mesodinium alive could have any doubt as to the identity of the organisms described by Darwin, and it would be very hard to improve his verbal description.