158 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



the girdleless and anteriorly biflagellate Prorocentrum, and the Dinifera, which 

 received the forms with "dinoflagellate" structure. The latter family he divided 

 into the three subfamilies Dinophysida, Peridinida, and Gymnodinida. The de- 

 scriptive appellations Adinida and Dinifera introduced by Bergh have been em- 

 ployed in one form or another in the classification of the Pyrrophycophyta down 

 to the present. 



One of the most important advances in our knowledge of the structure of 

 the dinophycid cell since the time of Ehrenberg was made by Klebs in 1883. 

 He established that in freshwater forms the alleged transverse band of cilia 

 actually is a single flagellum that lies in the transverse groove. A year later 

 (Klebs, 1884) he established that this is true also of marine forms. A second 

 significant contribution made by Klebs (1883) was concerned with the nucleus. 

 He described the jointed structure of the chromatin threads and recognized the 

 systematic value of this feature. It will be recalled that Allman in 1855 had 

 already noted this condition (an observation which appears to have been over- 

 looked by Klebs), but it is through the work of Klebs that this peculiarity was 

 first brought into focus. 



Klebs in 1883 believed that the Dinophyceae were thallophytes but that they 

 occupied a seemingly isolated position among them. In 1884 he was inclined to 

 think that these organisms might be related to some of the other yellow 

 flagellates. 



Confirmation of Klebs's observations, both with respect to the single trans- 

 verse flagellum and the structure of the nucleus, came forth quickly through 

 the work of Biitschli (1885). In Bronn's Klassen und Ordnungen des Thier- 

 Reichs, Biitschli (1883-1887) also gave a comprehensive treatment of the Dino- 

 phyceae, including an excellent review of the history of knowledge of the group. 

 In consequence of the new information concerning the flagellation, Biitschli 

 abandoned the name Cilioflagellata given to these organisms by Claparede and 

 Lachmann and substituted the designation Dinoflagellata (whorled flagellates?) 

 which has remained as the popular name of the assemblage. Recent observations 

 by Deflandre (1934) indicate, ironically, that the transverse flagellum of Gleno- 

 dinium uliginosum bears a single row of cilia. 



The first formal recognition of the dinoflagellates as a group of plants came 

 in 1890 and 1892 when AVarming (1890)*^ and Engler (1892) accepted them 

 as a subdivision of the thallophytes. They were henceforth always included in 

 treatises on the algae or the plant kingdom as a whole. 



An outstanding monograph on the structure of the cell in marine dinoflagel- 

 lates was published bj^ Schiitt in 1895 as part of the results of the Plankton 

 Expedition, and in 1896 the same author presented an excellent systematic treat- 

 ment of the group, with the exception of certain forms such as Noctiluca and 

 Polykrikos which were excluded. Schiitt (1896) divided the group into three 

 families: (1) the Prorocentraceae, which included the terminally biflagellate 

 forms, (2) the Gymnodiniaceae, which received the athecate forms with dino- 

 flagellate organization, and (3) the Peridiniaceae, in which he placed the thecate 

 forms with dinoflagellate organization. 



6. According to Warming (1890, p. V) the dinoflagellates were first accepted as algae 

 by Petersen and himself in 1889 in their Grundtrak af Forelcisninger over systematisk 

 botanik for medicinske og farmaceutiske studerende. 



