Studies on a Marine Parasitic Ciliate 



375 



ciliate cells and was not confined to the supernates. Further 

 work has to be done to prove this fact beyond doubt. 



Table 4 gives one example of an experiment where infected 

 KB cells have served as food. Four logs of virus were present 

 at time as found in the KB controls. A heavy inoculum of ciliates 

 was used to insure a fast destruction of KB cells in order to pre- 

 vent virus production beyond the level present at time (time 

 when cihates are introduced). One sees that the feeding and 

 multiplying ciliates did not destroy the virus seed at 30 C. 

 There was, as would be expected, less ciliate growth at the 

 higher temperature, which on the other hand favors polio multi- 

 plication. We are not prepared at the present time to state 

 that the rise of titre in the 35 C cultures was due to true virus 

 production carried out by the ciliates. A few undestroyed KB cells 

 could have been responsible for this newly formed virus. 



TABLE 4 

 Exposure of Ciliates to Polio Infected Mammalian Food Cells (KB Line) 



time 



After 24 Hours of Incubation at 



30°C 35°C 



Log Log 



Cil/ml LogTCD/ml Cil/ml TCD/ml Cil/ml TCD/ml 



7.7 



7.5 



141,000 



440,000 



4.3 



105,000 

 200,000 



5.7 



To eliminate any doubt about the nature of newly formed 

 virus, we made use of a feeder cell which cannot support polio- 

 virus production. Such an experiment is shown in table 5. We 

 started with a lower inoculum allowing for a 48 hour experimental 

 time. This resulted in an 80 fold increase of the feeding popula- 

 tion. Here we encountered the drop of infectivity caused by fish 



