252 THE BIOLOGY OF STENTOR 



loose of the granules and the pellicle was shed in pieces, not as a 

 hull, as in the amazing demonstration with Blepharisma by Nadler. 

 Shedding of the pellicle was especially noticeable and clear-cut in 

 NH4CI, ammonium acetate, LiCl, and egg albumen (Fig. 70A). 

 Stentors apparently regenerate both pigment and pellicle when 

 returned promptly to culture medium, for their later appearance 

 was altogether normal. The concentrations employed were usually 

 1%, made up in the filtered lake water used for culturing. Attempts 

 by repeated treatment with salts to obtain stentors which were 

 completely devoid of surface pigment granules and could not 

 recover them later were not successful. Granules located in the 

 endoplasm (Weisz, 1949a) may have been mobilized (and 

 multiplied) to take their place. 



These shedding responses might therefore be useful in tracing 

 the origin of the pigment granules during their rapid regenera- 

 tion, as well as in testing the consequences for respiration of greatly 

 reducing the number of cortical granules. And treatments causing 

 a neat shedding of the pellicle should provide a means of studying 

 the significance of this layer in permeability as well as in 

 immunological reactions. 



II. Shedding of the membranellar band 



In addition to producing extrusion of pigment, Prowazek's 

 (1904) ^% solution of table salt caused the shedding of the mem- 

 branellar band in coerideus; Daniel (1909) obtained such cast-offs 

 with glycerine. These reports were generally neglected until, 

 independently, I found the same effect when stentors were sub- 

 jected to 25% sea water (Tartar, 1957a). I then tested several 

 chlorides, sulfates, acetates, sugars, urea, and albumen — usually 

 in 1% solution. All produced sloughing of the membranellar band 

 with one exception. This was ethanol in which, as in the studies of 

 Daniel, the membranelles remained completely intact and beating 

 as the last part of the cell to disintegrate. In all treatments which 

 produced sloughing, the animals could later recover and regenerate 

 the feeding organelles, with the single exception of NiS04 treat- 

 ment. The typical response was for the stentors to swim about in 

 agitation, backwards in the monovalent cations, then suddenly 

 contracting as if the agents had succeeded in penetrating deeply. 

 Following this contraction, the membranelles became fimbriated 



