MORPHOLOGY AND PHYSIOLOGY OF GENUS URONYCHIA 355 



scalpel. Careful study of the fragments made the exact plane 

 of cutting certain. In all cases the normal sister cell was kept 

 as a control, and if for any reason it did not live and divide, the 

 experiment was not listed as successful. Individuals experi- 

 mented on were kept until they died or else divided. Drawings 

 were made from life of some of the more interesting cases. 

 Stained preparations were made for the study of nuclear 

 conditions. 



Specimens to be stained were put upon a cover-slip which had 

 been smeared with a small amount of egg albumen and then a 

 drop of the killing fluid added. The best killing fluid was found 

 to be a saturated solution of bichloride of mercury in absolute 

 alcohol. As soon as the specimen was stuck to the cover-slip 

 it was put into a dish of the killing fluid and left for five minutes. 

 It was then transferred to 95 per cent alcohol and then to water. 

 Most of the individuals were stained with Heidenhain's haema- 

 toxylin, the short method. This gave most excellent results, 

 for it not only stained the nucleus clearly, but it demonstrated 

 the cirri as well. No other stain showed the new cirri in divid- 

 ing individuals as sharply. Acid fuchsin, methylene blue, and 

 Mallory's triple stain were used with indifferent success. 



For the study of sections the following method gave satis- 

 factory results. Uronychia transfuga was found in abundance 

 in the zoogloea scum of old culture dishes. The only other hy- 

 potrich of the same size found here was a Euplotes. The scum 

 from one dish was removed by rolling it into a ball, which was 

 then fixed. Flemming's, Bouin's, Zenker's, and Schaudinn's 

 fixing fluids were used. In this way a number of Uronychia 

 could be handled together. This zoogloea was then embedded 

 in the usual manner and sectioned (5 n) . Iron haematoxylin and 

 Mallory's triple stain were used. The best results were obtained 

 with Zenker's fixation and iron haematoxylin. 



DESCRIPTION OF THE GENUS URONYCHIA (STEIN) 



Diagnostic characters: medium-sized, colorless hypotrich with 

 a constant body form; body oval, rigid, truncate anteriorly, 

 somewhat rounded posteriorly ; peristomal fossa broad and deep. 



