Cytology and Movements of the Cyanophyceae. 315 



for the movements of these organisms. Pfitzer (63) has 

 raised the objection to it, that the velocity of osmotic cur- 

 rents would be so slow as not to cause motion. This is cer- 

 tainly a valid objection, notwithstanding the explanation of 

 Kozlowski (43) that "the cause of movement does not lie 

 in the velocity of the current, but exclusively in the change 

 in position at the centre of inertia, and is equally true 

 whether liquid flows out through macroscopical or molecular 

 openings." Hansgirg's efforts (35) to show such currents 

 were made by placing Oscillaria filaments in almond oil. 

 In this way he found that there was a delicate pellicle of 

 water surrounding the organism which was sufficient in 

 some cases to cause motion for four days, when the layer 

 of water would finally be broken up and the movements 

 cease. Such an experiment, it would seem, would be a 

 stronger argument against osmotic currents than for them, 

 notwithstanding the efforts of the supporters of this theory 

 to make out that the movements are very slight, even if they 

 look very great on account of the magnification used. When 

 we magnify the movements we also magnify the organism, 

 and the relation between the two remains the same. Thus 

 how the very thin pellicle of water which remains surround- 

 ing the trichomes when placed in the almond oil, can be 

 sufficient to set up osmotic currents of such magnitude as to 

 cause motion, either oscillating or creeping, of several times 

 the diameter of the plant, is difficult to understand, as is 

 likewise how the delicate, hydroscopic pellicle on the trich- 

 omes of the Oscillariese growing on moist soil can cause 

 movements over the surface of the supporting substratum as 

 claimed by this author, for the delicate film of water sur- 

 rounding them as they creep is many times thinner than the 

 diameter of the trichome, though the motion passes through 

 many times that distance. 



The ingenious ideas of Wolle and some others con- 

 cerning these movements being caused by the multiplication 

 of cells, are also similar theorizings without any basis in 



