TECHNIQUES 347 



algas develop, and I can confirm this. As nutrient, Stolte (1922) 

 used the scum from lettuce infusions, or beef extract. He found 

 the presence of algae useful, but I think this was because his cul- 

 tures were quite putrid or over-rich and therefore oxygen deficient. 

 Wheat and barley grains, boiled to prevent germination, are 

 satisfactory (Hyman, 1925, 193 1; Weisz, 1948c). The addition of 

 dry leaves and reeds was recommended by Peters and I have 

 simulated this by adding desiccated lettuce, but without 

 conspicuous advantage. 



Stentors are to be provided with food organisms. Very likely 

 stentors can accumulate and ingest bacteria but the eating of larger 

 organisms should be more efficient. The following organisms have 

 been observed to be eaten and digested by stentors: 



Colpidium 



Blepharisma 



Paramecium hursaria 



Minoidium, and other colorless flagellates 



Small rotifers 



Chilomonas 



Halteria 



Tetrahymena 



Glaucoma 



Gonium^ and other colored flagellates. 

 With the least trouble, cultures can be inoculated with these 

 organisms, but for cleaner and more abundant cultures the food 

 organisms should be grown separately. Burnside (1929) fed 

 coeriileus on Halteria grown separately with hay or malted milk. 

 Constant cultures fed with Colpidium were set up by Hetherington 

 (1932a). Schwartz (1935) grew his animals in filtered pond water 

 plus soil extract and fed them on Colpidium grown separately in a 

 0-03% solution of yeast extract. Chilomonas with Paramecium were 

 recommended as food by Turner and Brandwein (1937). Stentors 

 cannot readily capture Paramecium caudatum so that smaller and 

 less vigorous species are recommended. Gerstein (1937) and 

 Dawson (1953) used Blepharisma grown separately and obtained 

 long-enduring cultures. I also found Blepharisma to be excellent 

 food; but the pigment of this ciliate has a photodynamic action 

 (Giese, 1957) which might prove damaging under bright illumina- 

 tion during operations on stentors which have ingested them. 



