20 



NORMAL HISTOLOGY. 



Anaphases : 



Migration of segments {Metakinesis}. 



Segments pass towards the poles of the new nuclei. 



Equatorial plate produced by massing of migrating segments. 



Separation of segments into polar groups. 



Appearance of connecting filaments. 

 Daughter- Wreaths, or Asters. 

 Telophases : 



Beginning division of cell-protoplasm. 

 Daughter- Skeins : 



a. Loose skein. 



b. Close skein. 



Completion of new nuclei. 

 Acquisition of nuclear membranes. 

 Reappearance of nucleoli. 

 Completed separation of cell-protoplasm. 

 Resting Daughter-Nuclei. 



Fission of the nucleus is ordinarily followed by cleavage of the 

 protoplasm, the resulting new cells being entirely distinct elements. 



A deviation from this usual 

 procedure is, however, some- 

 times encountered where the 

 division of the nucleus has 

 not been followed by cleavage 



FIG. 13. 



FIG. 12. 



B D 



Segmenting ova of ascaris megalocephala : A , cell Large marrow-cell : the nu- 



contains nucleus, two centrosomes (c), surrounded by cleus has undergone repeated 



attraction-spheres, and adherent polar body (/) ; B, division without cleavage of the 



beginning polar striation around the centrosomes and protoplasm, 



attraction-spheres ; C, cell viewed from polar field, the 

 striation proceeding from the centrosome ; D, cell seen 

 from the side, apices of nuclear spindle correspond with 

 centrosomes. (After Boveri.) 



of the cell-protoplasm, the latter remaining undivided even after the 

 repeated division of the nuclei. Examples of such ' ' endogenous' ' 

 formation are seen in the multinucleated giant marrow-cells. Not 

 infrequently under such conditions the nucleus undergoes repeated 

 abortive division, resulting in the production of irregular lobulated 

 or cleft forms embedded within the common protoplasmic mass. 



