MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 17 



cannot be considered satisfactory, because he does not allow enough importance to 

 the fact that we are dealing with cysts. 



Evitt & Davidson (1964), Deflandre (1962) and Norris (1965) have cogently stated 

 the taxonomic problem that arises because so little is known about the encystment of 

 living species of dinoflagellates. Currently the classification of living species and 

 genera is based on the tabulation and appearance of the motile stage cell, but it is 

 now known (Evitt & Davidson 1964) that similar motile stages can produce grossly 

 different cysts and an extensive reclassification is likely to ensue when more work has 

 been done on encystment. It is therefore unsatisfactory to press fossil cysts into a 

 taxonomic system based largely on living motile stages as Eisenack has done, when 

 we know so little about the life cycles and important reclassification of the living 

 forms is impending. 



The frequent dissimilarity between the motile and cyst stages means that attribu- 

 tion of a cyst to a species based on a motile stage can only be confidently asserted on 

 the direct evidence of cultures or on the circumstantial evidence of close geographic 

 association of certain cyst types with certain motile stage types. Neither of these 

 possibilities is available to the palynologist who at the most can hope to identify a 

 fossil cyst with a Recent one by morphological comparison. In an overwhelming 

 number of instances he can expect to find no exact counterpart, and his classification 

 must be a classification of cysts. 



It is hoped to deal more thoroughly with the classification of fossil dinoflagellate 

 cysts in a separate publication where the whole range of cyst types can be considered 

 adequately. 



