348 THE BIOLOGY OF STENTOR 



3. Survival on slides 



Although Balbiani (1889) reported keeping one stentor alive on 

 a slide for nearly a month with feeding, most students since 

 Johnson have found that stentors isolated into a few drops or even 

 into watch glasses do not long survive. In fact, one gains the 

 impression that the results of many investigations may have been 

 compromised by poor survival on slides and the unfavorable 

 conditions this implies. We have noted, however, that stentors 

 will multiply and clones can be started in deep depression slides 

 containing only about i ml. Hetherington (1932b) was able to 

 maintain stentors for a year in Stender dishes, a few dozen to 

 the dish. 



Exploring the limits of isolation culture, I kept a normal 

 coeruleus for 41 days in 3 drops of medium with some feeding and 

 two transfers to fresh fluid, together with the addition, after 

 3 weeks, of two squashed stentors which I thought should supply 

 what stentors need. Experimental animals which had been 

 operated on in various ways survived as long as 16 days in 3 drops, 

 but as a rule stentors live only about one week under these condi- 

 tions. It is quite possible that improvements in isolation culture 

 can be made, and the advantages of adding some stentor brei is 

 indicated. In any event, if specimens or controls do not survive 

 for at least two days, I regard the experiment unreliable. 



4. Staining 



More or less standard methods have been used for the cytological 

 study of stentors, and suggestions regarding fixation and staining 

 are given in the papers of Johnson (1893), Schwartz (1935), 

 Randall and Jackson (1958) and especially of Weisz (1949a, 1950a). 

 Diff"ering from most other ciliates, stentors have not revealed a 

 neat silver-line system either by the wet or dry methods of silver 

 staining (Villeneuve-Brachon, 1940; Weisz, 1949a). Merton (1932) 

 made a valiant effort to fix and stain stentors in the extended state, 

 but I am inclined to agree with Johnson that semi-contracted 

 animals are good enough for most purposes. To see the form of 

 extended stentors living animals are the best. Treatments which 

 have been used for anaesthetizing the contractile elements have 

 already been discussed in Chapter XIV. 



