Micro st omidae 149 



i-day old infusion, and allowed to stand at io° to 14° C. for 1 day. Then 

 the ripened infusion is inoculated with Colpidia, placed in a 9-inch petri 

 dish, and allowed to stand for 4 days. After this time the culture is 

 centrifuged for 30 seconds at 1800 revolutions per minute. The Col- 

 pidia form a dense, almost solid mass at the bottom, where they may 

 be separated from the supernatant fluid and the middle layer of debris. 

 The concentrated Colpidia should then be diluted to about 15 cc. with 

 1 -day old rye infusion. 



Stenostomum incaudatum may be cultivated in isolation pedigree lines 

 by placing one Stenostomum in a single drop of this fluid on a depres- 

 sion slide. Temperatures of 20 to 2 6° C. are favorable. The culture 

 fluid should be renewed daily, by transferring one Stenostomum to a fresh 

 slide with fresh, concentrated Colpidium fluid. Mass cultures may be 

 reared in similar rye infusion to which heavy growths of Colpidium have 

 been added. These cultures must be renewed before the supply of 

 Colpidia gets low. 



References 



For the culture of Stenostomum see also pp. 136 and 142. 

 For the culture of Catenula see p. 136. 



Family Microstomidae 



THE CULTURE OF MICROSTOMUM 



M. Amelia Stirewalt, University of Virginia 



MICROSTOMUM is particularly sensitive to very small traces 

 of such poisons as are used in chemical reagents. In the selec- 

 tion of glassware to be used in the culture of these animals, therefore, 

 care must be taken that dishes, pipettes, etc., have had no contact with 

 fixing and staining reagents. Petri dishes have proven most successful 

 as aquaria because the large, flat, bottom surface presents ample space 

 for the benthal habits of Microstomum. In these dishes the animals may 

 easily be seen with the naked eye, especially if the culture is placed over 

 a dark background. Both stender dishes and larger culture dishes, 

 however, will serve as aquaria, though the small capacity of the former 

 necessitates frequent change of the culture medium, and the large size of 

 the latter makes close observation of particular animals impossible. 



Into the aquarium selected, in the approximate proportion of 9-1, place 

 spring water (from a non-limestone district) and water containing small 

 detritus from the bottom of the stream or pond in which the Microstoma 

 were collected. It is best that no animals be present which can be seen 

 with a magnification of 20. To this medium may then be added such 

 Cladocera as Cypris, Daphnia, and their relatives [see pp. 207-220], and 



