360 JULIA ELEANOR MOODY 



ally in length, while the anterior region is drawn out to form 

 the narrow, compressed neck truncated obliquely at the tip. 

 Although cultures of Spathidium were kept under observation 

 from February 24 to July 7 through two hundred and eighteen 

 generations, no conjugation was observed. Attempts were made 

 to bring about this phenomenon by transferring numbers of 

 Spathidium to small dishes according to the method of Calkins 

 ('04) but without success. 



5. Encystment 



Encystment takes place either for the purpose of protection 

 against conditions adverse to the well-being of the organism 

 or for the purpose of reproduction. During a period of one 

 month attempts were made daily to cultivate Spathidium in 

 dishes of greater capacity than the Syracuse watch-glasses. 

 Staining dishes 3 cm. in diameter and 2 cm. in depth proved 

 fairly satisfactory for a short time, very few encystments occur- 

 ing during the first two or three days. But although given a 

 sufficient amount of hay-infusion and fed with a rich culture 

 of Colpidium at twenty-four-hour intervals, every individual 

 had encysted at the end of the fourth day. All attempts to 

 cultivate Spathidium in dishes larger than those described re- 

 sulted in encystment within twenty-four hours. 



To show the process of encystment the following experiments 

 were tried. On March 24, 1911, stock in good condition was 

 transferred to four Syracuse watch-glasses, some of it being 

 kept as control. To all four dishes was added an equal amount 

 of hay-infusion prepared twenty-four hours previously. With 

 a pipette a small quantity of the Colpidium culture was trans- 

 ferred to watch-glass A. To watch-glass B a quantity of Col- 

 pidium equal in amount to the culture of Spathidium transferred 

 was added. In both cases cysts were formed within twenty-four 

 hours. To watch-glass C and D a medium quantity of Colpidium 

 was added. Culture C was left over night close to the window 

 where the temperature was considerably below room temperature. 

 In the morning every individual was encysted. Culture D 

 was placed on the edge of the table near the radiator at 8 o'clock 



