158 



PROTOZOOLOGY 



Fig. 61. Development of spindle and astral rays during the mitosis in 

 Barbulanympha, X930 (Cleveland), a, interphase centrioles and centro- 

 somes; b, prophase centrioles with astral rays developing from their distal 

 ends through the centrosomes; c, meeting of astral rays from two cen- 

 trioles; d, astral rays developing into the early central spindle; e, a later 

 stage showing the entire mitotic figure. 



In Holomastigotoides tusitala (Fig. 172, a, b), Cleveland (1949) 

 brought to light the formation of the achromatic figure, and the 

 minute structure and change in chromosomes (Fig. 62). In the late 

 telophase, after cytoplasmic division, the centrioles follow the flagel- 

 lar bands 4 and 5 for 1.5 turns (a). The two chromosomes are an- 

 chored to the old centriole. When the new centriole has become as 



