356 CHAP. XXXI. INCLINATION AND EXCITATION 



were as i8 : 21, or i : 1-31, the mean ratio from the two 

 experiments being i : 1-27. These various results all tend 

 to show that the excitation is greater at 135° than at 45°. 

 In the following table the readings at 45° are those at the 

 beginning and at the end of the series of observations, the 

 reading at 135° being the intermediate one. 



Table XXX. —Excitatory Reactions at 45° and 135°. 



These very definite results tend to prove that the ecto- 

 plasmic layer is not uniformly irritable at all points, but 

 that it is more excitable at the apical end than at the basal 

 end of the cells. 



Summary 



Geotropic reaction is found to vary approximately with 

 the sine of the angle of inclination. 



The results of numerous experiments carried out by the 

 Method of Vertical Rotation tend to show that the excitatory 

 reaction at a large angle of inclination is relatively greater 

 than the value deduced from the law of sines. This suggests 

 the inference that the excitability of the ectoplasmic layer 

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

 at the basal end. 



This conclusion is confirmed by the fact that the excita- 

 tory reaction at 135° is about i-2 times greater than that 

 at 45°. At 45° the starch-grains accumulate at the basal, 

 and at 135° at the apical, end of the cells. 



