SPIROSTOMUM AMBIGUUM 403 



tap-water. In the stronger solutions the Spirostoma died 

 almost immediately, whilst although those in the weakest 

 solutions lingered for a few days, they showed no signs of 

 multiplying and ultimately locomotion was suspended and 

 disintegration followed. 



During his work upon Spirostomum teres, Maupas (19) 

 fed the material upon a solution of flour in water, which he 

 added to their own pond water. In order to find out whether 

 a similar medium would suit Spirostomum ambiguum, 

 0-150 grm. of flour was added to 100 c.c. of tap-water and 

 boiled for ten minutes, these being the amounts used success- 

 fully by Calkins (4) for U r o 1 e p t u s m o b i 1 i s . Varying 

 volumes of this solution were added to culture dishes and 

 to test-tubes which contained Spirostoma together with 

 pond-water and a little debris. No marked success followed 

 this experiment. In two cases the test-tube cultures lived for 

 some days but no division was seen. Mixtures of flour, hay, 

 and pond-water in various proportions, and solutions of Lemco 

 and Vitmar were all in turn tried without any success. 



Pond-water, together with the slimy, decaying leaves from 

 the bottom of ponds, was boiled for about ten minutes in order 

 to free it from any organisms which might be present. The 

 boiled leaves were placed into test-tubes with about 10 c.c. 

 of the water in which they had been boiled. The tubes were 

 tilled up with pond-water boiled to free it from any organisms. 

 At first approximately 2 c.c. of Woodruff's standard hay 

 infusion was added. This hay infusion was cooled and then 

 allow^ed to stand open to the air for twenty-four hours before 

 it was added to the cultures. By this means the hay infusion 

 was inoculated with a plentiful supply of bacteria. That it is 

 necessary to use newly made infusions is shown by the work of 

 Peters (25), who showed that the maximum development of 

 bacteria in a hay infusion is reached in approximately the first 

 three days. Further, Hargitt and Fray (10) have isolated from 

 old hay infusions many kinds of bacteria which are toxic to 

 Paramoecium. It is not improbable therefore that these old 

 infusions contain bacteria wdiich are toxic to other ciliates as 



