CHAPTER IV. 



THE FORMATION OF NEW CELLS. 



43. There are two essentially different ways in which 

 cells originate, viz., (1) by the division of a protoplasmic 

 body into two or more bodies ; (2) by the union of two or 

 more protoplasmic bodies. 



44. Cell-Formation by Division. The simplest cases of 

 the formation of cells by division occur in the Myxomy- 

 cetes. The swarm-spores (a, Fig 25), Avhich are naked masses 

 of freely moving protoplasm, first lose their nuclei (as in Z>), 

 and then become constricted (as at c) ; the constriction 

 deepens, and finally dhides each mass 

 into two parts (d, e,f). 



45. This may be taken, as the 

 type of cell-formation by division, 

 and in no case does it differ in any 

 essential particular from this. Most 

 plant-cells, however, are surrounded 

 by a Avail, whose deportment during 

 division enables us to distinguish two 



begun *./, completion of less well-marked modes of 

 the P rocess.-Aftcri>e Bury, cell-form ation by division. On the 

 one hand the wall divides as Avell as the protoplasm (Fission}, 

 while on the other the wall takes no part in the division, and 

 it is only the protoplasm which divides (Infernal Cell-For- 

 mation}. 



46. The best examples of Fission are to be seen in those 

 unicellular plants which have been frequently described 

 under the name of Protococcus.* "The cell elongates and 

 the protoplasm divides into two across its longer axis, and 



Fig. 25. Division of the 

 swarm-spores of C'fioniModer- 

 mu di/onne ; a, with nucleus ; 

 6. nucleus dlMolved ; c. two 

 nuclei, division of protoplasm 



ee "Huxley and Martin's Biology," Clinp. II. 



