xviii Introduction 



was alive with splendid examples of typical paramecia, 

 white in color, which showed plainly the details of structure. 

 Along the sides of the glass, just below the surface of the 

 water, a white ring was visible to the naked eye, which 

 under the lens was seen to be composed entirely of these 

 paramecia, and the sides of the jar were also covered with 

 colonies of Stentor polymorphus. In many cultures since 

 then I have obtained these rings of paramecia. From 

 such rings, hundreds of specimens may easily be transferred 

 to the slide by means of a camel's-hair brush or a medicine 

 dropper. 



Paramecia are also likely to be found in many small 

 aquaria ; they are often abundant in those in which clams 

 have been kept. But they can be studied to much better 

 purpose when they are so abundant that one can have 

 the large typical specimens in quantity. 



The course of the food-balls in the body may be admir- 

 ably shown by this method : place a lot of paramecia in 

 a watch glass with a small quantity of water ; add a little 

 powdered carmine to the water ; cover, and examine fresh 

 specimens at intervals of ten minutes for an hour or more. 

 You will be able to trace the whole course of the food-balls 

 in this way. 



The nucleus of Paramecium may be brought out by 

 staining with iodine, magenta, methyl-green, or other stains. 

 The trichocyst threads may be brought out by running 

 under the cover glass a dilute solution of osmic, picric, or 

 acetic acid. The form of the body is sometimes well 

 shown when Schultze's solution is added. 



Paramecia should be first studied under the low powers 

 with little or no cover-glass pressure. The normal shape 

 can then be seen. The pressure of the cover glass flattens 

 the body.' By placing a little cotton-wool beneath the 



