GENERAL CHARACTERS 71 



staining, a small rounded nucleus has been shown to exist 

 near the centre of the cell. 



The cell-wall is so thin that it is difficult to be sure of its 

 presence unless very high powers are employed. It can 

 however be easily demonstrated by staining yeast with 



vu 



C.U' 



X. x 



E 



E 



FIG. 13. Saccharomyces cerevisite. 



A, a group of cells under a moderately high power. The scale to 

 the left applies to this figure only. 



B, several cells more highly magnified, showing various stages of 

 budding, vac, the vacuole. 



C, a single cell with two buds (bd, bd') still more highly mag- 

 nified : c.w, cell-wall : vac, vacuole. 



D, cells, crushed by pressure : c.iv, the ruptured cell- walls : flsm, 

 the squeezed out protoplasm. 



E, E', starved cells, showing large vacuoles and fat globules (/). 



F, F', formation of spores by fission of the protoplasm of a starved 

 cell : in F the spores are still enclosed in the mother-cell-wall, in F 1 

 they are free. 



magenta, and then applying pressure to the cover-glass so as 

 to crush the cell. Under this treatment the cell-walls are 

 burst and appear as crumpled sacs, split in various ways and 

 unstained by the magenta (D, c. /), while the squeezed-out 

 protoplasm is seen in the form of irregular masses (pis///) 

 stained pink by the dye. 



