1 6 OF YEAST GERMS. 



examined it will be found to be composed of two 

 different kinds of matter, the one smooth, transparent 

 and external, forming a membrane closed at all points, 

 and commonly known as the cell wall (formed ma- 

 terial), the other soft, diffluent, also transparent, 

 but apparently composed of semi-fluid matter (ger- 

 minal matter or bioplasm]. If the yeast cell be firmly 

 pressed between glass plates it will burst, and the 

 contents will be squeezed out as soon as the rupture 

 of the protecting envelope has been effected. This 

 envelope or cell wall varies in thickness in different 

 cells, being firm and thick in the oldest, and so thin 

 as to be demonstrated with difficulty in the youngest 

 cells. The envelope itself is formed not by the de- 

 position of matter from the surrounding medium upon 

 the surface of the cell, but from the soft diffluent 

 bioplasmic matter within. This envelope is thickened 

 by the formation of new formed material from the 

 bioplasm which is deposited layer within layer upon 

 the inside of the already formed capsule, cell wall, 

 or envelope (Fig. 9 a, plate II.). The germinal or living 

 matter or bioplasm, can be coloured with an ammo- 

 niacal solution of carmine, while the formed material 

 remains perfectly colourless. This fact is shown in 

 the figures which have been coloured so as to resemble 

 the specimens from which they have been carefully 

 copied (see Plate I., figs. 6, 7, 8 ; plate II., figs. 9 to 12). 

 Of the production of the minute Yeast Germs. Now, 

 how are the little buds or offsets or gemmules of the 



