846 CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL-PERTILITY, xii., 



does not destroy the ciliates completely, as tested by nitrate hay- 

 infusion, or one-fortieth as tested by Giltay's solution. Inci- 

 dentally, they also show that nitrate hay-infusion is better suited 

 for the growth of ciliates, and Giltay's solution for the growth of 

 amoebae. 



The influence of the soil-moisture upon the action of the dis- 

 infectant, points to the ciliates either existing in the moist soil 

 in the motile state, or, if encysted, to the cyst-membrane being 

 more pervious to the combined action of moisture and toluene. 

 The age of the cyst may be a controlling factor. Recently 

 encysted ciliates and amcebae are delicate and colourless, while 

 the older ones are more or less brown and look undoubtedly 

 stronger. One can imagine that the destruction of the delicate 

 cyst may be an easy matter compared with the stronger. 



In the belief that a knowledge of the effect of heat might 

 throw some information upon the action of the volatile disin- 

 fectants, a series of examinations was made upon the appearance 

 and the activities of protozoa after they had been heated at 

 different temperatures. Cultures of protozoa in Giltay's solution 

 were taken up in capillary pipettes, and after the end had been 

 sealed, they were heated in water for ten minutes at different 

 temperatures. The pipette was then cooled, the point broken 

 off, and the suspension blown upon a slide and examined. 



Paramcecium was either still or moved about slowly after 

 having been heated at 39' or 40°. At 41°, it became quite 

 still, with the cilia moving slowly. At 42°, the organisms were 

 completely broken up into masses of debris. Colpoda cucullus 

 behaved somewhat differently, according to the size of the cells. 

 At 39°, some of the smaller or younger organisms were slowly 

 motile, others had stopped moving about the field, but the cilia 

 still vibrated; others were more or less spherical, with an ex- 

 truding slime-drop. At 40°, they were all non-motile, mostly 

 rounded, with a lateral slime-drop. This extrusion of slime 

 occurs during rapid encystment. Heated at 41°, they were all 

 rounded, and some appeared to have burst. The nuclei of the 

 rounded cells stained with methylene blue, the rest of the cell 

 did not take up the colour, from which it is inferred that the 



