CELL DIVISION 



briefly as follows : In the beginning of this phenomenon, the 

 nucleus, which plays the most important role, grows larger. 

 Its chromatin greatly increases, becomes contorted so as 

 to form a dense convolution, the close skein, or spireme. 

 Then the chromatin fibrils further thicken, become less con- 

 voluted and form irregularly arranged loops, the loose skein. 



Close Skein 



(viewed from the 



side); Polar field. 



Loose Skein 



(viewed from above i. e., from 

 the pole). 



Mother Stars 



viewed from 



the side). 



Mother Star Daughter Star 

 (viewed from above). 



Beginning. Completed. 



Division of the Protoplasm. 



FIG. 2. Karyokinetiq figures observed in the epithelium of the oral 

 cavity of a salamander. 



The picture in the upper right-hand corner is from a section though a dividing 

 egg of Siredon pisciformis. Neither the centrosomes nor the first stages of the 

 development of the spindle can be seen by this magnification. X 560. (From 

 Brubaker.) 



During the formation of these skeins the nuclear membrane 

 and the nucleoli disappear. The fibrils of the loose skein now 

 separate at their peripheral turns into a score of loops, the 

 closed ends of which point toward a common center a clear 

 space called the polar Held. When seen from above these 

 loops of chromatin make a wreath, called the mother wreath; 



