125 



(whether mutually deviating or not) of thaseparate flagellar beatings. 



The movement of the flagella, which had hitherto been established 

 in the choanocytes, was a rowing-movement (as Fig. 56fiJ, 57 rf, 

 58 &) ; so a motion which is not peculiar to the long flagella but 

 to the short cilia of the protozoa; while, on the contrary, the 

 flagella of the unicellulars are moving in spiral-lines (compare 

 DOFLEIN 17). If the latter, now, could be proved to be also the 

 case with the choanocytes, than the solution would be quite easy. 

 For the spiral- or screw-motion of the flagellum of the unicellu- 

 lars pushes the water on, just as the screw of a steamer, in the 

 direction of and turning round the axis of the flagellar spiral, 

 either towards the cell (Flagellata) or in the opposite way 

 (spermatozoa). — This is simply determined by the fact, whether a 

 spiral wave (optically) moves on from the top to the base of the 

 flagellum or in the opposite way; but I will not enter further 

 into this question here. — If in the choanocytes the motion of 

 the flagella took also place in this manner (as a spiral), it is a 

 matter of fact, that by the action of all choanocytes of a flagel- 

 lated chamber together there should be a constant flow of water 

 either from the centre of the chamber towards the wall or from 

 the wall towards the centre, provided that the spiral-motions of 

 all choanocytes moved on in the same way. We would how- 

 ever not have anything to do with their synchronism or their 

 direction. Now, according to Doflein (17) the Choanoflagellata 

 push the water off along the axis of the flagellar spiral. Might 

 it not be possible then that the same should count for the cho- 

 anocytes too? 



The question was therefore to observe the movement of their 

 flagella under circumstances that were as normal as possible. On 

 the other hand one had to claim, that the study of the flagellar 

 motions and of the water-current, produced by as many choano- 

 cytes together as there are within a flagellated chamber, had to 

 be preceded by an accurate research into the motion of the fla- 

 gellum of one, isolated, choanocyte and into the water-current it 

 caused in a free and open space. 



Now, I can state that I have succeeded in both ways. The study 



