STUDIES IN THE LIFE-HISTORY OF EUGLENA.. 323 



of them in order to secure material for detailed study. It has 

 been found however, that a wide variation exists in the type of 

 culture medium required for the different species, and that when 

 one says a culture medium has been discovered for Euglena the 

 statement means little unless the species is indicated. 



A small amount of green scum known to contain Euglena, found 

 on the surface of a culture of pond water, leaves and grass, was 

 placed in a large petri dish containing one liter of tap water and 

 one gram of malted milk. An abundance of active Euglenx were 

 produced in a few days and identified as Euglena agilis. From 

 this original culture all the material for my sub-cultures used in 

 the investigation were secured. 



The most satisfactory culture medium for this species has been 

 found to be split pea infusion made by boiling forty split peas in 

 one liter of tap water. Sufficient citric acid is added to keep 

 down extensive growth of bacteria. For keeping cultures in an 

 inactive condition, quince seed jelly as recommended by Turner 

 (1917), has been used. This medium has also been satisfactory 

 for the study of the animals in the living state under the micro- 

 scope. Inoculation of split pea infusion with material from the 

 quince seed jelly produces abundant active forms within a few 

 days. 



Various killing fluids have been used, the best results being 

 obtained with Schaudinn's fluid heated to 56 degrees Centigrade. 

 Other fluids used were Flemming's strong, Bouin's picro-formol 

 solution, chrom-acetic-osmic mixture, Zenker's fluid and osmic 

 acid vapor. 



For staining, aqueous iron-alum hsematoxylin, long method, 

 has given the most satisfactory preparations. The use of a 

 counter stain has aided in the study of the motor apparatus. 

 Eosin and bordeaux red (.1 per cent, solution for 24 hours before 

 mordanting) have given the best results. All figures have been 

 drawn from material counter-stained with eosin. 



Other stains used were Delafield's haematoxylin, safranin and 

 light green, Flemming's triple, Borrell's stain, and iron alum 

 haematoxylin counter stained with light green or orange G. 



The organisms were killed at different times during the day, the 

 most satisfactory material being secured from eight to twelve 



