386 Louise Hoyt Gregory 



was made of a depression slide; two glass supports held the cover 

 glass over the hollow center, covering an area that would hold 

 about twenty drops of liquid. These slides were kept in moist 

 chambers, which were subjected to ordinary room temperature. 

 All possible care was taken to prevent contamination. The slides 

 were washed in boiling water, supports and covers were kept con- 

 stantly in water, when not in use, and the cloths used in drying 

 were for that purpose only. Capillary pipettes were used for the 

 transference of the individuals, and these were kept separate from 

 those used for other purposes. A large pipette was used expressly 

 for the filling of the chambers. 



Both living and fixed material were studied. The living indi- 

 viduals were isolated by means of a fine pipette and studied in a 

 hanging drop. Material was fixed at frequent intervals, and sec- 

 tions as well as total mounts were made. For embedding methods 

 see Calkins ('07). The best fixative was found to be a saturated 

 solution of corrosive sublimate, to which had been added 10 per 

 cent formalin solution in the proportions 10 : lOO cc. saturated 

 solution. The least shrinkage resulted with this method. For 

 staining the total mounts, Heidenhain's haematoxylin, and 

 haemacalcium, gave the best results. Eosin and picro-carmine 

 were farily good stains. Delafield's haematoxylin, safFranin, eosin 

 and methylene blue, were tried, but the results were not good. 

 The sections cut 5 microns in thickness, were stained in general 

 with iron haematoxylin, both with and without the counter stain 

 of eosin. Other stains were tried, but none proved to be satis- 

 factory. 



Ill MORPHOLOGY AND PHYSIOLOGY 



Tillina magna is a large ciliate having the shape of a bean or a 

 kidney. Gruber in his description states that the average length 

 is 200/f, and that he often found larger forms. In only a few cases, 

 however, have I found it measuring even 200/z in length, and never 

 more than this, the size varying from ioo-200/z in length, and from 

 70 to 1 80// in breadth. The average length and breadth of fifty 

 individuals was i6o/x and ioo/< respectively. The anterior half 

 of the body is broad and blunt, the posterior half tapering. The 



