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. While this is going on the nucleus passes to the surface 

 of the cell and divides, one of the products of fission remaining 

 in the mother-cell, the other in the bud. The bud increases 

 in size {bd') until it forms a little globular body touching 

 the parent cell at one pole : then a process of fission takes 

 place along the plain of junction, the protoplasm of the bud 

 or daughter-cell becoming separated 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- 

 colo7iies 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 



