92 Phylum Protozoa 



There is a tendency toward an over-accumulation of bacteria both 

 in the cultures and in the stock supply. The stock supply may be filtered 

 through several layers of cheesecloth to remove excess bacterial accumu- 

 lations. The material in the culture dishes may be poured off frequently 

 and some of the filtered material added. 



CULTURING ARCELLAE 



Bruce D. Reynolds, University oj Virginia 



ARCELLAE may be cultured in a hay infusion as follows: 

 Place 10 grams of clean timothy hay in a clean pyrex beaker 

 containing 250 cc. of distilled water (pH 6.8). Heat to boiling point 

 and allow to boil slowly for 5 minutes, then strain through two thick- 

 nesses of cheesecloth and store in quantities of about 3 cc. in small, ster- 

 ile, hard glass test tubes. The tubes should then be plugged with cotton 

 and placed in boiling water for 15 minutes. After 2 days they should be 

 subjected again to boiling for the same period of time in order to kill 

 any bacteria which may have escaped the first sterilization by being in 

 the spore stage. The medium in these tubes constitutes the stock solu- 

 tion and will keep for months without deterioration provided evaporation 

 does not take place. 



In making up the culture medium take 1 part of the stock solution 

 and add to it 9 parts of distilled water (pH 6.8), giving a 10% hay 

 infusion. After the tube containing some of the stock solution has 

 been opened and a part of its contents used the remainder should be 

 discarded. 



Using the medium prepared in the above manner Arcellae may be 

 cultured in hollow-ground slides over a long period of time in a constant 

 medium. The culture medium should be changed every day or two and 

 the depression slides should be kept in a moist chamber placed in sub- 

 dued light. 



References 



For the culture of Arcellae see also pp. 74 and 134. 

 For the culture of Arcella vulgaris see p. 60. 



Family difflugiidae 



METHODS OF CULTURING TESTACEA 



A. B. Stump, University of Virginia 



Difflugia oblonga (D. pyrijormis), small varieties [see also p. 136] ; 

 D. lobostoma and D. constricta, small varieties; and Lesquereusia 

 spiralis may be cultured almost indefinitely by using a number of the 



