CYTOLOGY OF SACCHAROMYCES CERVICI/E. 439 



success, and eosin and orange G were found to be equally use- 

 less. 



Fixation in corrosive-acetic-alcohol slightly shrinks the cells 

 and gives the chromatic material in the cytoplasm such great 

 affinity for basic stains that in most cases the nucleus is obscured. 

 After fixation in Bouin's it does not stain so heavily and the 

 nucleus can be seen in all cases, providing it is not too heavily 

 stained. The successful technique finally developed was fixation 

 in Bouin's and staining before the picric acid was completely 

 washed out. This decreased the affinity of both nuclear and 

 cytoplasmic chromatic material for stain, especially the latter. 

 In this way the nucleus could be stained without showing the 

 chromatic bodies in the cytoplasm at all. This procedure made 

 possible a careful study of the nuclear chromatin both at rest 

 and during division. Light green was found very valuable for 

 the study of the metachromatic granules. Even when they are 

 very abundant this stain will demonstrate their granular nature. 

 In preparations in which no counterstain or the other acid stains 

 are used they frequently appear as a single, large mass. 



It was found that fixation and staining in carbol fuchsin 

 followed by light green furnished an excellent method for demon- 

 strating the alveolar nature of the cytoplasm. Although the 

 nucleus could be seen in these cells its minute structure was not 

 visible and the method is of no value for the present work. 

 Light green is taken up by the gelatinous secretion sometimes 

 given off by the yeast cells and consequently furnished a good 

 means of demonstrating the presence of this substance. 



MORPHOLOGY. 



Saccharomyces cervicix is a round to slightly oval yeast whose 

 size ordinarily ranges from 5 to 10 micra. In old cultures the 

 cells are occasionally elongated, sometimes crescentic (Fig. 7). 

 The cell is enclosed in a thin though distinctly evident wall. 

 This wall occasionally becomes greatly thickened and the cells 

 pass into a very resistant stage (durable cells, chlamydospore) 

 such cells can be kept dry for a year without destroying their 

 viability (Figs. 10 to 13). 



One of the most prominent structures inside the cell is the 



