MITOSIS OR KARYOKINESIS 205 



division were connected with the nucleus. It was shown that 

 the chromatin of the nucleus during vegetative stages is dis- 

 tributed in the form of granules on a network of achromatic 

 3naterial called linin (Fig. 88, A) that these granules collect and 

 coalesce in one or more spirally wound threads of chromatin 

 called the spireme (Fig. 88B,c ) ; that these spireme threads divide 

 longitudinally throughout the entire length and that the double 

 spireme then segments into a number of short double rods called 

 chromosomes (Fig. 88, D, E). It was discovered that the num- 

 ber of these chromosomes is always the same in individuals of 

 the same species and all types of the tissue cells of the same indi- 

 >dduaL At the same time it was shown that the chromosomes 

 collect in the center of a peculiar spindle-formed body derived 

 from achromatic material of the cell and having characteristics 

 peculiar to itself in the form of centrosomes at the poles of the 

 spindle and spindle fibers running from one centrosome to the 

 other (Fig. 88, D,E, r). It was found that these centrosomes 

 arise by the division of a single centrosome lying on the periph- 

 ery of the nucleus and separation of the daughter-centro- 

 somes through an arc of 180; also that the nuclear membrane 

 disappears at this time while new fibers (mantle fibers) 

 grow out from the centrosomes and connect with the chro- 

 mosomes. It was seen that the two equal parts of each 

 chromosome were then' separated from one another, each 

 half going toward one of the two centrosomes so that the 

 ( ntire mass of chromatin material is equally divided between 

 the two daughter-nuclei which are formed by new nuclear 

 membranes (Fig. 89, G, H, i, j). It was noted finally, 

 that nuclear division is completed by disintegration of 

 the daughter-chromosomes into the distributed chromatin 

 granules characteristic of the vegetative nucleus, and that after 

 this nuclear division the cell body divides by a plane passing 

 t hrough the center of what was the nuclear division figure. 



This complicated chain of processes with its involved activity 

 c f chromatin, centrosomes and spindle fibers was named karyo- 

 Hnesis by Schleicher 1878, and mitosis by Flemming 1882, and 

 I oth names are found in current literature. 



