REPRODUCTION 



137 



chromatin becomes irregularly disposed in a reticulum; swelling 

 continues and the chromatin condenses into a twisted band, a 

 spireme, which breaks into many small segments, each composed of 

 large chromatin granules. With the rapid development of the spindle 

 fibers, the twelve bands become arranged in the equatorial plane 

 and condense. Each chromosome now splits longitudinally and two 

 groups of 12 daughter chromosomes move to opposite poles and 



m m 



feSsS^iaSt 



Fig. 63. Mitosis of the micronucleus of Conchophthirus anodontae, 

 X2640 (Kidder), a-c, prophase; d, e, metaphase; f, g, anaphase; h, i, 

 telophase. 



transform themselves into two compact daughter nuclei. In Zeller- 

 iella intermedia (Fig. 64), Chen (1936) saw the formation of 24 

 chromosomes, each of which is connected with a fiber of the intra- 

 nuclear spindle and splits lengthwise in the metaphase. While in the 

 majority of protozoan mitosis, the chromosomes split longitudinally, 

 there are observations which suggest a transverse division. As exam- 



