— 163 — 



Bruno Schröder in an appendix to Seligo : Untersuchungen in 

 den Stuhmer Seeen, Danzig 1900, mentions the bristles of Pedia- 

 strum on pag. 75, but he only remarks that they do exist and that 

 the matter is very imperfectly examined. 



Ghodat speaks about similar bristles in his paper: Algues 

 vertes de la Suisse 1902. (Beiträge zur Kryptogamenflora der Schweiz) 

 (pag. 50), and fig. 152 (pag. 228) shows a single Pediastrum cell with 

 its bristles. He does not quote any of the preceding treatises and 

 therefore he has probably discovered the bristles himself. 



Finally in 1903 O. Zacharias gives a reply to Waldvogel in 

 Biologisches Gentraiblatt XXIII pag. 593— 95; 1903. Here he esta- 

 blishes that tufts of bristles are really to be found on the cell pro- 

 cesses of Pediastrum duplex Meyen, clathratum A. Br. and reticula- 

 tum Lagerheim. 1) because he has sometimes been able to see 

 them without desiccation, by extraordinarily good illumination. 

 2) He thinks the desiccation method to be sufficiently good since it 

 is also employed to show the bristles on Rhizosolenia longiseta and 

 Atheya Zachariasi. 3) Finally he remarks that some very able 

 investigators, after examining into the material transmitted to them 

 have affirmed the phenomenon. He mentions also that E. Lemmer- 

 mann has described a bristled form of each of the named species of 

 Pediastrum. (forma setigera Zach.). 



At last he says that the Pediastra found in plankton very 

 often have no bristles at all. He states especially after researches 

 in about 100 seas and ponds in Holstein, that he did not find any 

 at all any more than at the Pediastra from Plön. He therefore 

 supposes that the bristles only are developed under very particular 

 circumstances and perhaps only exist at certain seasons of the year. 



Methods of investigation. 



The method originally applied by Zacharias to make the brist- 

 les visible by a simple desiccation [Zacharias 1899], has not turned 

 out to be of such general appliance as those mentioned in the 

 sequel. The figures obtained by his method are far from being 

 so clear and distinct as those yielded by the others and often, 

 where I, following the other methods, could point out bristles, I 

 could not see them in the desiccated preparations. 



The methods used are essentially the same as those used for 

 showing the cilia of bacteria, viz: partly the generally used 



11* 



