THE NEW CELL DOCTRINE 15 



Although the nucleus changes comparatively little during 



the progressive division of the cell, yet during the division of 



the cell matters are 



very different, for 



during every cell Hsa*w "?M^W 



*- ** - t&> 



cleus passes 

 through wonderful 

 t r a nsf ormations. * 

 During these 

 transform ations 

 the sharp limits of 

 the nucleus disap- 

 pear, and the nu- 

 clear substance 

 gathers together 

 in small masses to 

 which we apply 

 the name chromo- 

 somes. Each 

 chromosome di- 

 vides, and one 

 piece of each 

 chromosome 

 tributes to 

 formation of one of 



FIG. ii Red blood cells of an embryo duck in vari- 

 ous stages of division. The pictures show the origin, 

 COn- division and migration of the chromosomes, the spindle, 

 the t ^ ie reconst ^ tutlon f tne daughter nuclei after the division 

 of the cell bodies. After M. Heidenhain. Magnified 



2300. 



the new nuclei; the 



other piece to the formation of the other nucleus. This process 



may now be found exactly described in the text-books. Every 



* Reference to the so-called direct division of cells, or amitosis, is intentionally 

 omitted. This form of division is rare, and the consideration of it is unessential 

 for our present purposes. 



