66 ENCYSTMENT AND EXCYSTATION OF AMOEBA 



ploying cysts which had been freed from living 

 bacteria by means of hydrochloric acid (2 percent.). 

 The cysts were taken from the same culture, and 

 in every case excystation was later than in controls 

 made with liquefying bacteria, and in some of the 

 former, which grew slowly, very few living amcebse 

 could be seen at the end of a week. These results 

 at least indicate that some of the bacterial products 

 necessary for excystation may be of the nature of 

 ferments similar to those which are capable of 

 liquefying gelatin. 



Excystation induced by the soluble remains of the 

 dead bodies of bacteria. To determine if excysta- 

 tion occurred in the absence of any stimulus from 

 without, cysts in pure mixed culture with B.fluor- 

 escens liquefaciens on an agar slope were treated 

 with 2-per-cent. HC1 for twenty-four hours, which 

 kills the bacteria, and were then washed thoroughly 

 with sterile water, the cysts, plus dead bacteria, 

 being placed on fresh plain 2-per-cent. agar media. 

 After a few days a few living amcebse were found, 

 but only in places where they were surrounded by 

 dense masses of dead bacteria. The vast majority 

 of cysts were quite unaffected. In order to find 

 if the accompanying dead bodies were responsible 

 for the excystation that occurred among the few 

 cysts, three live slides were prepared as follows : 



In (A) pure water was circulated through the 

 slide. In this way the dilution of soluble products 

 was so great that no excystation took place during 

 the whole period of observation (one week). In 

 (B) a solution of 0'1-per-cent. choline hydro- 

 chloride. No excystation took place, and no 

 difference from A was detected. In (C) a sterile 



