Introduction xvii 



excellent condition for study. Water from such a situa- 

 tion may be placed in jars indoors, and allowed to stand 

 some time with good results. 



THE PARAMECIUM 



Paramecia may commonly be developed by putting an 

 excess of pond-scum or other water plants in a vessel 

 containing water and setting the vessel in a warm, dark 

 closet for a week. There will then probably be a whitish 

 film on top of the jar; in this film you are likely to find 

 an abundance of paramecia. Keep the jar in a warm, 

 dark situation and they will continue to develop for some 

 time. 



One of the finest lots of paramecia I have ever seen 

 was developed in the following way ; a cylindrical jar 

 holding about two gallons (six inches wide by about fifteen 

 inches high) was nearly filled with water and then was 

 stocked with a mass of CEdogonium and other fresh-water 

 algae, obtained from a spring, October 22. An excess 

 of this was put in, and the jar was placed in a well-lighted 

 room, six feet from a window. Five days later a rather 

 thick film had formed on the top ; it contained an abun- 

 dance of large bacteria of various forms, a number of 

 ciliate and flagellate protozoa, a few desmids and diatoms, 

 as well as an occasional protococcus-like form. The sides 

 of the jar showed bacteria, desmids, diatoms, Protococ- 

 cus, Haematococcus, and a few euglenae. The bottom 

 showed an abundance of the same forms. After this 

 examination (October 27) I covered the jar and put it 

 in a dark closet. On November i another examination 

 was made. The white film showed many ciliate infusoria, 

 including some fine paramecia. Ten days later the water 



