PARASITIC PKOTOZOA FOUND I-V S. AFRICA. I'-V-y 



four aiiiiuais were <>-eiierally obtainable each week from tlie 

 post-mortem liall. The mu>cle of the apex of the yentricle was 

 found to be most convenient for examination. Sarcocysts 

 (Mieseher's tubes) were not usually seen in the smear-prepara- 

 tions of heart muscle, but free spores (Rainey's corpuscles) 

 occurred. Attention was concentrated on the spore stage. 



Beg-innino- in April. 1919. it was found that the spores of 

 S. teiielhi in the sheep were regularly seen for about four 

 months, but apparently became very few or absent during- the 

 latter half of July. During August and September and the 

 earlier part of Octobei', 1919, the spores were rarely seen. 

 During November, 1919, and onwards to May, 1920, tbe spores 

 were again regularly seen, and usually found to be numerous. 



A seasonal variation seemed to be indicated, the spores of 

 Sarcocystis teiiella appearing- to be relatively few or even 

 absent in the heart muscle of sheep during the colder montlis 

 of June, July and August. — which are winter months in South 

 Africa — ^but showing a very slight increase in numbers during 

 tlie montlis of Sei)tember and Hciobei^ — which are spring and 

 early summer months in South x\frica. Tbis was tlie inference 

 drawn from tlie observations made during 1919. The winter of 

 1920 has been sliglitly milder, and — continuing the record of my 

 observations up to September, 1920 — ^tlie spores of <S'. tenelhi 

 appear to have been rather more numerous during the winter 

 of 1920 than during that of 1919. The animals examined were 

 nearly all adults. These observations are not yet complete and 

 are being continued, but the available eA'idence goes to show 

 that spores of S. fenella in the heart muscle of sheep examined 

 near Pretoria are less numerous in the winter and spring or 

 early summer than in the middle and late summer. 



Similar observations on the Sarcocijsti.^ of cattle have been 

 commenced, and so far the results obtained a})pear to be 

 somewhat different. 



Seasonal variation is an example of i)eriodicity in nature. 

 The occurrence of such periodicity is probably much more 

 geneial and of greater imi)ortance than has hitherto been 

 suspected . 



It is interesting to note the results of J. W. Scott 

 (December, 1918), ■' who has been working on >S'. fenella in sheep 

 in the Northern Hemisphere, namely, on the Laramie Plains, 

 Wyoming, Ignited States of America. He finds that infection 

 is seasonal, the infections being' less numerous in the winter 

 and spring. He v orked on sarcocysts, and the period of 

 incubation after infection before sarcocysts appeared in the 

 muscles was from four to six weeks. He states that ewes become 

 infected year after year in successive seasons and that the 

 life-cycle falls under seasonal control. Scott's researches are 

 not yet complete. 



IXFL'SORIA. 



A number of C'iliata have been found in the alimentary 

 tracts of T^ngulata, especially in Uie rumen and reticulum of 



* Journ. Parasitology (Urbana), v, j). 45. 



