Boeck: Studies on Giardia Microti 



97 



the mode came on October 31. The depression period between the 

 first two cycles of encystment was two days in length during which no 

 cysts were found in the faces. The next period of cysts in the faeces 

 was only two days in length, November 3 to 5, and four cysts were 

 counted on each of these two days. No cysts were then found for 

 five successive days when on November 10 and 11 one cyst only was 

 found. A depression period of two days with no cysts precedes the 

 last cycle of encystment, which was continuing when the last exam- 

 ination was made, to form another mode. The intervals between 

 modes one, two, three, and four are 3, 2, 7, and 4 days, respectively. 



25 20 27 2S 29 30 31 1 



The interval between the last mode and incomplete mode on November 

 21 is six days. 



Rat 11. The first two periods or cycles of encystment were of 

 short duration and the number of cysts was never high. The first 

 cycle took place from November 1 to 3 and two cysts were counted 

 on each day. A depression period of five days followed this cycle 

 and no cysts were found in the faeces. The next cycle, from November 

 8 to 12, although longer than the first cycle, contained only a small 

 number of cysts. The mode of this cycle appeared on November 9. 

 Another mode is designated on November 15, which may be a true 

 mode since a period of depression follows it for two days, or this 

 portion of the cycle may be a part of the period of cysts in the faeces 



