ANALYSIS OF STENTOR 245 



dure was odd, as he did not count the smaller individuals ! But if 

 anything this should mask the strength of the results produced, 

 and hence we are merely left with the suggestion that possibly KCl 

 may supply an impulse to division. The effect, if valid, was 

 apparently not due to osmotic pressure, because lactose solutions 

 of even higher osmotic tension were without effect. 



7. Changes in state of the protoplasm 



An incidental observation of Prowazek (19 13) was that sodium 

 taurocholicum causes the endoplasm of stentors to clump into 

 balls and the nucleus, at first highly refractive then disappears. 



Changes in the internal viscosity of stentors in relation to various 

 ions was studied by Heilbrunn (1928). Centrifuging the animals 

 in various salt solutions he observed the relative speed with which 

 internal granules and particles passed through the endoplasm. 

 Bivalent cations (calcium and magnesium) apparently decreased 

 the viscosity of the interior, producing liquefaction. Monovalent 

 ions (K, Na, NH4, Li) increased the viscosity and caused coagula- 

 tion. But later Heilbrunn (1943) admitted that calcium, on rapid 

 entrance into the cell, could produce gellation instead of liquefac- 

 tion. Precisely what was happening in these experiments is 

 therefore not clear. 



Heilbrunn also studied in coeruleus and in Arbacia eggs what he 

 called the surface precipitation reaction, or the formation of films 

 over crushed cells which prevents their explosive dissolution. 

 Calcium appears to be necessary for this reaction, presumably a 

 type of coagulation, for no film formation occurred when the 

 calcium was removed with ammonium oxalate. (Schmitt, as quoted 

 by Moore (1945) states that calcium has more affinity for water 

 than protein polar groups and therefore desolvates these groups 

 which then join with others to produce a more solid state.) 

 Magnesium could not replace calcium in this reaction but strontium 

 could. That cells do not supply their own calcium for this reaction 

 he explained by conceiving that intracellular calcium is bound 

 and not free. 



Noting the difficulties of studying eflFects on the endoplasm by 

 simple immersion of a cell. Chambers and Kao (1952) micro- 

 injected solutions into the interior. Among other subjects was a 

 *' large variety " oi Stentor, quite possibly Wrw/^w^. They injected 



