Not 



IX. 



.-;,:> 



between n = l - 49 and n = 1'54, with an absolute minimum — 

 which is zero — about 1*51; the illumination reappears the further 

 that one departs from this zone in either direction. 



The following tables bring together the chief points in these 

 experiments : — 



1. Adoral cilia of Stentor polymorphus :— 



Inilex Nt of 

 the Liquid. 



Liquid employed. 



Degree of Illumination 

 of the Object. 



Comparison of the 



Indices of the 

 Liquid Xl and of 



the Object N,|. 



2. Reversible preparation : the same Stentor was followed 

 through a series of liquids : — 



36 

 53 

 66 

 53 



1-36 



Liquid. 



Ethyl-alcohol. 



Oil of cloves. 



Monobrornide of naphthaline. 



Oil of cloves. 



Ethvl-alcohol. 



Illumination. 



Distinct. 

 Practically nil. 

 Distinct. 

 Extremely faint. 



Faint, but distinct. 



3. Reversible preparation : Vorticella: — 



4. Desiccation has the same effect on the cilia of Protozoa as 

 on epithelial cilia — the illumination is quite destroyed ; this again 

 confirms the depolarisation hypothesis. 



