18 



NORMAL HISTOLOGY. 



achromatin spindle to each of the groups, thus insuring an accurate 

 and equal division of the original chromatin between the new nuclei. 

 The chromatic segments, becoming further aggregated about the 

 equator of the nuclear spindle in their migration, form a compressed 

 mass, known as the 



(7) Equatorial plate.* As the newly-grouped fibrils pass out- 

 ward towards their respective poles, the free ends of the receding 

 segments become united by delicate threads of achromatin the 

 connecting filaments which stretch between the corresponding 

 limbs of the separating segments. With the completion of migra- 

 tion the cardinal features of the division of the nucleus have been 

 established, since the anaphases are but repetitions, in inverse order, 

 of the changes already instituted. Following the stage of the equa- 

 torial plate, the fibrils group themselves about the poles of the spindle 

 and form 



FIG. 10. 



Diagram illustrating the migration and redisposition of the segments of chromatin, guided by the achro- 

 matic lines : A, mother-star; B and C, stage of equatorial plate ; D, daughter-stars. (After Rabl.) 



(8) The daughter-stars, or diaster, each of these corresponding 

 to a new nucleus. About this time the cell-protoplasm, which until 

 now has been almost passive, begins to exhibit a constriction of its 

 body, which impression now steadily progresses until the protoplasm 

 of the cell completely separates into the portions destined to become 

 the bodies of the cells, enveloping the new nuclei. The karyokinetic 

 cycle is completed by each 



(9) Daughter-wreath or star in turn assuming 



(10) The stage of the daughter-skeins, at first loose and afterwards 

 close; on obtaining nuclear membranes and the nucleoli reappearing, 

 the new nuclei finally pass into the stage of rest. 



* The term "equatorial plate" has been employed by some authors to indicate 

 the later phases of the aster stage. 



