96 



University of California Publications in Zoology [Vol. 19 



Kat 9. There are three distinct periods when cysts were found in 

 the faeces in this rat. This condition, we have seen, has been common 

 to many of the curves already discussed. The first period of cysts in 

 the faeces extended from October 29 to November 4. The number of 

 cysts. reached three in twenty fields at the mode on October 31. A 

 period of depression then took place, from November 4 to 12, during 

 which no cvsts occurred in the faeces. From November 12 to 15 is 



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25 26 27 28 29 30] 31 1 2 3 4' 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 



Rat 9 

 Fig. 8 



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Rat 10 

 Fig. 9 



the next period of cysts in the faeces, with the mode on November 13. 

 A period of depression of three days followed ; no cysts were counted 

 when the examinations were made. The cysts then appeared again 

 on November 18, on which day a third mode is reached. But as in 

 mode five^ shown in figure 7, mode three in this figure may have proved 

 to be a part of the rising curve following it, had the examinations been 

 continued for a few days longer. The intervals between modes one 

 and two and two and three are thirteen and five days, respectively. 



Rat 10. There are four modes representing the days when the 

 highest number of cysts were counted in four distinct periods. The 

 first period, October 29 to November 1, was three days in length and 



