106 BIOLOGY: GENERAL AND MEDICAL 



toward one pole of the nuclear spindle, until there has been 

 an exact separation of the nuclear material, one-half 

 having gradually moved into the polar field, the other 

 half into the-hypopolar field. 



This results in the formation of a double figure, the 

 amphiaster, or "daughter-stars." Each exactly resembles 

 the aster or mother-star except that its size is smaller. 



During this phase of the nuclear changes the cytoplasm 

 shows a constriction in the line of the equatorial plate 

 which progressively deepens, so that atfout the time the 

 nuclear changes are perfected the separation into two 

 cells is also completed. 



4. The Telophase, or the Transformation of Each Daughter- 

 Star into a Perfect Nucleus. This is accomplished by a 

 succession of events corresponding to those described as 

 characterizing the prophase, except that they occur in 

 the reverse order i.e., the chromosomes abandon their 

 star-like formation, adjust themselves to form a spirem, 

 become mixed with the linin filaments, and lose their 

 distinctness until the usual nuclear appearances are re- 

 sumed. 



This general outline of the cell division is, however, 

 subject to many modifications, necessitated by the sim- 

 plicity and complexity of the cells and the number into 

 which they divide. 



In those cells in which no nuclei can be discovered by 

 existing methods of examination, no nuclear changes 

 can be associated with division. The cell having grown 

 to a certain size, appears to separate into two or more 

 equal parts, each of which takes on an independent 

 existence. The structure of certain cells, as the bacteria, 

 is still controversial. Some believe them to have large 

 nuclei and see in them appearances analogous to those 

 of karyokinesis at the time of division. It is usual, 

 however, to describe the division of these organisms 

 as taking place by direct division, i.e., simple fission 

 without karyokinesis. 



