COLLECTION, CULTIVATION, OBSERVATION 883 



Ca 3 (P0 4 ) 2 0.002 gm. 



Pyrex water 1000 cc. 



Pelomyxa carolinensis. — These amoebae grow well in a finger bowl 

 with 150 cc. of redistilled water to which large numbers of Parame- 

 cium are added daily. Pace and Belda (1944) advocate the following 

 solution instead of distilled water: 



K2HPO4 0.08 gm. 



KH 2 P0 4 0.08 gm. 



CaCl 2 0.104 gm. 



Mg 3 (P0 4 ) 2 • 4H 2 . 002 gm. 



Pyrex water 1000 cc. 



Small mono- or di-phasic amoebae. — Musgrave and Clegg's me- 

 dium, modified by Walker, is as follows: 



Agar 2.5 gm. 



NaCl 0.05 gm. 



Liebig's beef -extract 0.05 gm. 



Normal NaOH 2 cc. 



Distilled water 100 cc. 



Arcella and other Testacea. — The testaceans commonly multiply 

 in a mixed culture for several weeks after the collection was made. 

 Hegner's method for Arcella: Pond water with weeds is shaken up 

 violently and filtered through eight thicknesses of cheese cloth, which 

 prevents the passage of coarse particles. The filtrate is distributed 

 among Petri dishes, and when suspended particles have settled down 

 to the bottom, specimens of Arcella are introduced. This will serve 

 also for Difflugia and other testaceans. Hay or rice infusion is also 

 a good culture medium for these organisms. 



Actinophrys and Actinosphaerium. — Belaf cultivated these helio- 

 zoans successfully in Knop's solution: 



Magnesium sulphate . 25 gm. 

 Calcium nitrate 1 gm. 



Potassium phosphate . 25 gm. 



Potassium chloride 0.12 gm. 



Iron chloride trace 



Distilled water 1000 cc. 



Freshwater dilates. — They are easily cultivated in a weak infusion 

 of hay, bread, cracker, lettuce leaf, etc. The battery jars containing 

 the infusions should be left standing uncovered for a few days to al- 

 ow a rich bacterial growth in them. Seed them with material such 



