PAPENFUSS: CLASSIFICATION OF THE ALGAE 157 



Ehrenberg observed the posteriorly directed flagellum but erred in usually 

 figuring this end of the cell as the anterior end. lie also failed to understand 

 the nature of the transverse flagellum, which he interpreted as a transverse band 

 (or at times as two transverse bands) of cilia. 



That the longitudinal flagellum is directed posteriorly was first pointed out 

 by Perty in 1852. He (1852) was also the first to call attention to the existence 

 of naked representatives of the group. 



In Gymnodinium xiherriyyium Allman in 1855 first observed the peculiar 

 structure of the luicleus in this phylum. Carter in 1858 confirmed an earlier 

 observation by Allman (1855) to the effect that these organisms at times formed 

 resting stages. Furthermore, he noted the division of the protoplast of resting 

 stages to produce new individuals, which circumstance, apparently more than 

 the fact that some of these beings possess chlorophyll, caused him to conclude 

 that dinophycids were plants rather than animals. Carter (1858) was also the 

 first to establish that the wall of dinophycids, at least as far as the resting stages 

 were concerned, is composed of cellulose. 



On account of the alleged presence of a transverse band of cilia, Claparede 

 and Lachmann (1858-1859) created a .separate order Cilioflagellata for the dino- 

 phycids, and regarded them as a connecting link between the flagellates and the 

 ciliates. To these authors goes the credit for first pointing out that the desmo- 

 phycid genus Prorocentrum is related to the dinophycids instead of the crypto- 

 monads where Ehrenberg (1838) had placed it. 



In 1872, Allmann expressed the view that the highly modified Noctiluca is 

 allied to the dinophycids. This luminescent genus had for a long time been asso- 

 ciated with the coelenterates and in 1873 Haeckel created for it the order Cystoflag- 

 ellata, but subsequent work has shown that Allman 's conclusion was well founded. 



In a paper devoted largely to investigations on bacteria. Warming in 1876 

 briefly referred to his observations on dinophycids. He announced the occur- 

 rence of cellulose in the wall of the motile stages of these organisms and thus 

 extended the earlier findings of Carter (1858) that the wall of resting stages 

 consists of cellulose. Warming also established that in these organisms food 

 is stored in the form of starch and that some of them possess a pigment similar 

 to that of diatoms. On the basis of these significant observations. Warming con- 

 cluded, as Carter (1858) previously had on much less secure grounds, that the 

 dinophycids were algae. 



A new era in the study of these organisms started with the publication in 

 1878 and 1883 of the first and second fascicles of the third part of Stein's Der 

 Organismus der Infusionsthiere. Stein not only gave the best systematic treat- 

 ment that had yet been presented of the group but illustrated them abundantlj^ 

 and with considerable accuracy. Some of his figures still rank among the best 

 that have been produced of the species in question. Stein regarded the Dino- 

 phyceae as animals and placed them (Stein, 1883) as a suborder, "arthrodele 

 Flagellaten" (articulated flagellates), in his order "Flagellaten." He divided 

 the suborder into the five families Prorocentrinen, Noctiluciden, Peridiniden, 

 Dinophysiden, and Cladopyxiden. 



During the period that Stein was studying these organisms, Bergh (1881) 

 also published a treatise on them. He regarded them as constituting an order 

 Cilioflagellaten which he divided into two families : the Adinida, which included 



