352 JULIA ELEANOR MOODY 



13 large numbers of very small Spathidia were found but no 

 Colpidia. Change in environment, therefore, would seem to 

 account for the appearance of the small transparent individuals 

 which have been observed in the original culture from October, 

 1911, to the present date. 



2. Material and methods 



While details of Spathidium spathula can be seen only with 

 a compound microscope, I found the binocular much more con- 

 venient to use. From a watch glass containing daughter cells 

 of one individual, three were selected on February 24, 1911, 

 and each transferred by means of a capillary pipette to a sepa- 

 rate glass dish. These dishes are 4 cm. square, 8 mm. deep 

 and possess a central, circular, shallow cavity, the capacity of 

 which is about If cc, or 80 drops. I have found these small 

 dishes invaluable for this work because owing to the clearness 

 of the glass and the gradual slope of the depression it is impossi- 

 ble for the organism to get into any part of the dish which cannot 

 be brought into focus. They are also more convenient to handle 

 than depression slides. These glass dishes were kept in a moist 

 chamber, a large glass stender dish 10 inches in diameter and 

 3 inches deep. 



After several trials with tap-water, pond-water and hay- 

 infusion, the latter was adopted as the best medium, prepared 

 according to the method of Calkins j('02) and used when twenty- 

 four hours old. In general, the hay-infusion was used undiluted, 

 but toward the end of the series a few drops of pond- water were 

 frequently added with satisfactory results. 



Each morning the number of divisions during the preceding 

 twenty-four hours was recorded and one individual from each 

 line isolated according to the following method: into one of the 

 small glass dishes containing six drops of undiluted hay-infusion 

 and one drop of Colpidium culture, a single Spathidium was 

 transferred by means of a capillary pipette, care being taken to 

 carry over as little as possible of the old medium. This ])re- 

 caution is necessary'' since the small quantity of fluid in the 

 depression dish soon becomes turbid with the accumulation of 



