74 SACCHAROMYCES LESS. 



in budding, the parent form does not, as in simple fission, 

 lose its individuality, becoming wholly merged in its twin 

 offspring, but merely undergoes separation of a small portion 

 of its substance in the form of a bud, which by assimilation 

 of nutriment gradually grows to the size of its parent, 

 the latter thus retaining its individuality and continuing to 

 produce fresh buds as long as it lives. 



Multiplication by budding goes on only while the Sac- 

 charomyces is well supplied with food : if the supply of 

 nutriment fails, a different mode of reproduction obtains. 

 Yeast can be effectually starved by spreading out a thin 

 layer of it on a slab of plaster-of-Paris kept moist under 

 a bell-jar : under these circumstances the yeast is of course 

 supplied with nothing but water. 



In a few days the yeast-cells thus circumstanced are found 

 to have altered in appearance : large vacuoles appear in 

 them (Fig. 1 2, E, E') and numerous fat-globules (/) are formed. 

 The protoplasm has been undergoing destructive meta- 

 bolism, and, there being nothing to supply new material, has 

 diminished in quantity, and at the same time been partly 

 converted into fat. Both in plants and in animals it is found 

 that fatty degeneration, or the conversion of protoplasm 

 into fat by destructive metabolism, is a constant phenomenon 

 of starvation. 



After a time the protoplasm collects towards the centre of 

 the cell and divides simultaneously into four masses arranged 

 like a pyramid of four billiard balls, three at the base and 

 one above (F). Each of these surrounds itself with a thick 

 cellulose coat and becomes a spore, the four spores being 

 sooner or later liberated by the rupture of the mother-cell 

 wall (F'). 



The spores being protected by their thick cell-walls are 



