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cilia-staining methods, partly the „dark-ground illumination". These 

 methods I shall very shortly indicate. 



1) The method used more than any other is Löffler's cilia- 

 staining method in Fischer's modification [Strasburger 1902 pag. 

 413]. This method is very simple and easy and done in the right 

 manner it gives fair and clear figures. It is* very important that 

 the mordant is not too long kept; it must not be older than 4—5 

 days. Speaking in the following about Löffler's method, without 

 any remark, I always mean this method in Fischer's modification. 



2) The silvering method of Van Ermengem [Arthur Meyer 1903 

 pag. 120] I have found to be very efficient and producing, in the 

 best cases, figures of extraordinary sharpness and clearness. But 

 the method is both expensive, as the mordant does not keep long, 

 and technically difficult to execute; therefore I have only tried it 

 and not employed it further. 



3) Zettnow's method is also a silvering method [Zettnow 1899 1 ; 

 it is more easy to employ than the last mentioned, and the figures 

 become clear without the inconvenient precipitations on the cover 

 glass, but the bristles appear to a high degree irregularly winded, 

 probably owing to the mordant. Therefore this method is also 

 used rather little. 



These three methods are all deficient in one respect viz. that 

 the organisms must be desiccated on a cover glass before the stai- 

 ning. This can not but disturb the natural conditions in several 

 ways, and the examined algæ coenobia lie always down in one 

 manner by the desiccation viz. the flat side down, and therefore it 

 always will be impossible by these methods to get a view of the 

 coenobia in any other position. 



4) Therefore trying to stain the bristles without desiccation the 

 tannic acid vesuvin used by Senn and Klebs [Klebs 1886 pag. 346 

 Note 4] occurred to me. For a long time it failed totally; but at 

 last I succeeded, especially when I took care that rapid currents 

 did not arise when the stain solution mingled with the water 

 wherein the algæ were placed, as these currents may make the 

 bristles invisible by bending them down round the algæ coenobia 

 or even tear them of. I used the following proceeding: On the 

 slide I put a little drop with as many specimens as possible 

 of the algæ that is to be examined. This drop I spread out 

 so that it in form and size nearly corresponds with the cover 

 glass. On the underside of this the stain solution is spread in a 



