7 6 



ELEMENTS OF BIOLOGY. 



O 



b. Gemmiparons Cell-multiplication. In this process new 

 cells are formed by little buds or outward processes, which 

 are thrown out by a parent-cell (fig. 22). Each little bud 



appears to consist of the 

 living matter or bioplasm 

 contained within the cell; 

 and it either thrusts out 

 a portion of the cell-wall, 

 or, as stated by Beale, 

 gains access to the ex- 

 terior by minute pores in 

 the limiting membrane of 

 the cell. The cells thus 

 produced may remain at- 

 tached to the parent-cell, 

 and may repeat the pro- 

 cess of gemmation ; or they may become detached to lead 

 an independent existence. 



c. Fissiparous Cell-multiplication. In this process a parent- 

 cell divides by cleavage or fission into two or four parts, 

 each of which becomes a perfect and independent cell. This 

 process is by no means so important as the two preceding, 

 and it is doubtful if it exists at all, except as a modification 

 of endogenous cell-multiplication, if we employ this term in 

 the wide sense in which it is used above. 



form of cytogenesis, in which new cells are produced in a parent-cell 

 round independent nuclei, without the nucleus of the latter dividing or 

 taking any share in the process. 



Fig. 22. Cells of the Yeast-plant, producing 

 fresh cells by a process of gemmation. 

 Magnified 2800 diameters. (After Beale.) 



