KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 101 



It was also due to the indefatigable labors of Ehrenberg (1854) that the 

 discovery of fossil dinoflag'ollates was made. These were mainly species of 

 Peridinlum present in tlie flints of Delitzsch, l)elonging to the Cretaceous. 



The next landmark in the history of the dinoflagellates was the appearance 

 of Stein's monograph in 1878. Between this date and the publication of the 

 work of Ehrenberg a few contributions were made, chiefly on the thecate forms. 

 Among these might be mentioned the investigations of Perty (1852) on the 

 fresh- water species in the Alps and their environs. A few of the forms he 

 described undoubtedly belong to the G}Tiinodinioidae, ])ut considerable doubt 

 attaches to them owing to the lack of adequate figures and descriptions. Also 

 of interest from a geographical point of xiaw is the work of Schmarda (1854) 

 on forms from the Nile River and neighl^oriug watei'S in Egypt. 



Of more unportance was the work of Claparede and Lachmann (1858-61), 

 both from a developmental as well as a morphological viewpoint. They estab- 

 lished the genus Amplildiniun} and recognized the dinoflagellate affinities of 

 the genus Proroccufrum. They were the first to note the encysted forms, par- 

 ticularly the secondary, crescent-shaped cysts of at least two different species, 

 one of which is undoubtedly Gymnodinium lunula. The flagellated organisms 

 were oriented by these investigators, as well as by Ehrenberg, with the longi- 

 tudinal flagellum projecting from the anterior end of the body — the reverse of 

 its actual relations but in keeping with the conditions found among other 

 flagellates. The transverse flagellum was also seen as a row of cilia extending 

 around the body. 



Claparede and Lachmann divided the Protozoa into four orders or tribes: 

 Ciliata, Suetoria, Cilioflagellata, and Flagellata. The Cilioflagellata comprised 

 the dinoflagellates and was based on their conception of the motor organelles 

 of these forms as consisting of both cilia and flagella. This conception of the 

 ciliate structure of the transverse flagellum was held by later investigators, as 

 Stein (1878), Bergh (1881&), and Saville-Kent (1880-82), until the work of 

 Klebs (1883) clearly pointed out the error of this interpretation. 



With the appearance of Stein's monograph (1878-83) a new era of investi- 

 gation on the flagellates was opened. In the twenty-five magnificent folio plates 

 with which his work is illustrated we find the only accurate representation of 

 the dinoflagellates that had been put forth up to this tune. His figures were 

 made with the high magnification of from 600 to 1200 diameters or more, hence 

 his analysis of the finer structures as well as the organization of the body, gave 

 an entirely new and adequate conception of these organisms, with the exception 

 of the transverse flagellum, which he still figured as a row of cilia. His work 

 is also notable for the num])er of new species which he added to the list of those 

 previously descri])ed. He estal)lished the genera llemidouum and Gymnodi- 

 iiitim among the non-thecate forms, Init the major part of his treatise relates 

 to the thecate dinoflagellates. 



