EXCYSTATION 63 



and it seems to act best when the alkalinity is 

 about 0*01 per cent. 



Excystation hastened by choline (hydrochloride). 

 Some experiments have already been carried out 

 by other authors with the object of artificially 

 producing excystation in the absence of living 

 bacteria with various tissue extracts and ferments, 

 although without much success. The following 

 data indicate that among bacterial products which 

 hasten the process of excystation, even if they do 

 not originate it, dilute solutions of choline (which 

 is a kinetic) are effective. 



Three live slides were prepared, and a number of 

 cysts from the same culture placed on each. Solu- 

 tions were employed as follows, and the results 

 observed at the end of twenty-four hours. 



(1) Distilled water. 



(2) Sodium chloride, 0'2 per cent. 



(3) Choline (old, containing neurine), 0'2 per 

 cent. 



After twenty-four hours : 

 In (1) very few have excysted. 

 In (2) none have excysted. 

 In (3) many have excysted. 

 The experiment was then modified as follows, 

 again using three slides at the same time : 



(1) Distilled water. 



(2) 0*5-per-cent. sodium bicarbonate. 



(3) Equal volumes of 0'5-per-cent. creatine and 

 0'2-per-cent. choline, the mixture beingmade alkaline 

 with soda bicarb, to 0'25 per cent. 



After twenty-four hours : 

 In (1) none have excysted. 

 In (2) a few have excysted. 



