Cell Division 



101 



SPINDLE. Regular movements of cliromo- 

 somes are possible only in the presence of a 

 spindle. This interesting structure originates 

 from the prophase nucleus. In most cells the 

 entire non-chromosomal material of the nu- 

 cleus seems to transform into the spindle, in 



others only part of the nuclear material is 

 used (Fig. lOA and B, whitefish blasto- 

 mere). Cytochemical evidence indicates that 

 spindle material appears in the nuclear sap 

 during interphase in cells that are preparing 

 for division (Sticli, '51a, b). The size of the 



■iiii 





Fig. 16. Types of mitotic spindles. A, First maturation metaphase in egg of Artemia (after Gross, '35). 

 B, Cleavage of Artemia (after Gross, '35). C, First spermatocyte metaphase in a coccid, Llaveia bouvari 

 (after Hughes-Schrader, '31). D, Oogenesis of Acroschismus (after Hughes-Schrader, '24). E, Early ana- 

 phase spindle in the radiolarian Aulacantha (after Borgert, '00). F, Second spermatocyte division of Gossy- 

 paria (after Schrader, '29). 



