ANALYSIS OF STENTOR 239 



Reversal of beating of the body cilia in unattached stentors is 

 immediately manifested in backward swimming in which the 

 effective stroke of the cilia is directed forward instead of backward. 

 Merton (1932, 1935) made an extensive study of the effects of 

 various salts and other substances in compelling stentors to swim 

 backward. The species used wcreroeseli, coeruleus, and polymorphus. 



First it should be mentioned that distilled water alone produced 

 backward swimming, with most of the animals disintegrating in 

 two hours. Peters (1908) had early shown this injurious effect of 

 pure water on coeruleus. He transferred the animals every 15 

 minutes to fresh distilled water and all then died within an hour, 

 death occurring not by swelling of the whole cell but by the forma- 

 tion of internal vacuoles w^hich increased in size and led to a 

 blistering of the surface with final disruption. Death he attributed 

 to washing out of the salts of the cell, but it may just as well have 

 been due to other osmotic effects; for Jennings (1902) found that 

 sugars killed by the subtraction of water and that there is no effect 

 at first but only after a sudden contraction, following which the 

 animals crumpled and decreased in volume. 



Therefore Merton made up his solutions in tap water which had 

 no effect on their behavior and was not immediately injurious. He 

 found that monovalent cations induced reversal of ciliary beating 

 while the bivalent cations of calcium and magnesium did not. Thus 

 weak solutions of KCl produced a continuous backward swimming. 

 Using their chlorides, the monovalent ions tested were in approxi- 

 mately decreasing order of effectiveness : K>Rb>Cs>Na>NH4. 

 Anions also had some effect on the response. Potassium compounds 

 were compared, and the order of decreasing effect of the anions in 

 promoting ciliary reversal was 



C03>S04>C1>I, NO3, P04>Br>Ac. 



I later confirmed these results in regard to contrasting effects of 

 monovalent and bivalent cations (Tartar, 1957a). In addition I 

 found that LiCl, which only produced disintegration of stentors 

 for Merton, also induced conspicuous backward swimming. And 

 ammonium acetate in strength of 1%, a compound not tested by 

 Merton, caused the most prolonged and continuous reversal of any 

 of the compounds used. 



