 In this case, the process consisted in the engulfment (incomplete phagocytosis) of the ciliate "M. rubrum" which in turn engulfed a whole cryptomonad and now only the plastids remain.There has been debate surrounding whether the plastids of "D. caudata" are permanent or kleptoplastids.It is now known that the plastids of "D. caudata" are kleptoplastids and the explanation for the discrepancy among molecular and ultrastructural data is due to structural modification during the acquisition of plastids through feeding.