vii GEMMATION 73 



The mode of multiplication of Saccharomyces is readily 

 made out in actively fermenting yeast, and is seen to differ 

 from anything we have met with hitherto. A small pimple- 

 like elevation (c, bd) appears on the surface of a cell and 

 gradually increases in size : examined under a high power 

 this bud is found to consist of an offshoot of the protoplasm 

 of the parent cell covered with a very thin layer of cellulose : 

 it is formed by the protoplasm growing out into an offshoot 

 like a small pseudopod which pushes the cell-wall before 

 it. The bud increases in size (bdf ) until it forms a little 

 globular body touching the parent cell at one pole : then a 

 process of fission takes place along the plane of junction, 

 the protoplasm of the bud or daughter-cell becoming sepa- 

 rated from that of the mother-cell and a cellulose partition 

 being secreted between the two. Finally the bud becomes 

 completely detached as a separate yeast-cell. 



It frequently happens that a Saccharomyces buds in 

 several places and each of its daughter-cells buds again, 

 before detachment of the buds takes place. In this way 

 chains or groups of cells are produced (B), such cell- 

 colonies consisting of two or more generations of cells, the 

 central one standing in relation of parent, grandparent, or 

 great-grandparent to the others. 



It must be observed that this process of budding or 

 gemmation is after all only a modification of simple 

 fission. In the latter the two daughter-cells are of equal size 

 and are both smaller than the parent-cell, while in gemma- 

 tion one the mother-cell is much larger than the other 

 the daughter-cell or bud and is of the same size as, indeed is 

 practically identical with, the original dividing-cell. Hence 

 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 



