INFLUENCE OF MAGNETIC FORCES ON STREAMING 



49 



tain substances which have different magnetic properties, and though all 

 are attracted (paramagnetic) when in water, the force of attraction differs 

 greatly. Hence it follows that, given a sufficiently powerful field, some 

 action, whether retarding, accelerating, or directive, must be exercised not 

 only upon growth, but also upon streaming. Negative results simply 

 indicate that the field is not powerful enough to overcome or modify the 

 other forces at work in the cell, and hence is unable to produce an exter- 

 nally perceptible result. The influence of magnetic fprces on growth must 

 be left for future solution, but the problem as to their effect on streaming 

 is more susceptible to attack, and has indeed already been answered in the 

 negative by Reinke (1. c.) in the case of Cliara. 



SECTION 18. Influence of Magnetic Forces on Streaming. 



No change in the plane of rotation, in the position of the indifferent 

 line, or in the direction of streaming was ever produced, however strong the 

 field might be. This is hardly surprising, when we consider that gravity 

 exercises no directive action on streaming, and that the magnetic forces 

 acting on the cell-constituents were always very much weaker than that of 

 gravity. The latter does, however, slightly influence the velocity of stream- 

 ing in large cells, but in a magnetic field, purely negative results were at 

 first obtained, the long axes of the cells being parallel to the lines of force, 

 and the pole-pieces two centimetres apart. Thus : 



Similar results were obtained with Nitella and Elodea, and little or no effect 

 was exercised even when the action was more prolonged. 



In the last case the quickening is possibly the result of a change of tempo 

 of internal origin, since it persists when the field is destroyed. 



1 Off no field, on = full field. The numbers are averages of from 6 to 10 observations of the 

 metronome beats made while the stream crosses a measured space. 



