SUMMARY 405 



Summary 



Direct electric stimulation of adequate intensity 

 induces a retardation of torsional response which may 

 culminate in actual reversal. 



Minimal electric stimulation, as well as moderate 

 stimulation of a subtonic specimen, induces enhancement 

 of the rate of torsion. 



Indirect stimulation causes an acceleration of the rate 

 of torsion. 



Sudden thermal variation acts as a stimulus and causes 

 retardation or even a reversal of direction of torsion. 



Mechanical stimulation induces retardation or reversal 

 of torsion according to the intensity of stimulation. 



Under diffuse stimulation by strong light the rate of 

 torsion undergoes diminution. 



Red light induces an enhancement of the rate of torsion, 

 while blue light induces a marked retardation. 



Geotropic stimulation has a definite influence on the 

 rate of normal torsion. When the stem is held inverted, 

 the rate of normal torsion undergoes a retardation which 

 may even culminate in an actual reversal of the direction 

 of torsion, proving that geotropic stimulation is more 

 effective in the inverted position. Facts have already been 

 adduced which show that the excitabihty of the ectoplasmic 

 layer at the apical end of the geo-perceptive cells is greater 

 than at the basal end. In the inverted position the heavy 

 particles, which are supposed to cause geotropic excitation, 

 press against the apical ends. The retardation of torsion 

 in the inverted position thus offers a further confirmation 

 of the statolith-theory. 



