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THE AMEBIC AN NATURALIST 



[Vol. LIV 



Janssens's first figure). At this stage where the inner 

 strands come into contact they are represented as fusing 

 with each other at three nodes. The threads may next be 

 supposed to flatten against each other to make the con- 

 jugated threads keep their spiral configuration and 

 then condense to make the thick threads. In this condi- 

 tion they pass to the equator of the spindle or they may 

 begin to open out before they reach the equator, Fig. 7 B. 



If the first division is reductional for every part of the 

 thread, the halves of the thread move apart in opposite 

 directions, and as a consequence of the way the twisted 

 threads have flattened against each other this opening 

 out may produce rings lying in different planes, Fig. 7 

 D, not necessarily at right angles to each other, but at an 

 angle with each other. 



The rings are assumed to be due to the reductional 

 separation of the segments of the chromosomes along the 

 tetrad, but the further movements of the daughter chro- 

 mosomes after they have reached the equator of the 

 spindle must be referred to another mechanism that now 

 comes into play, namely, the forces that carry the chro- 

 mosomes to the poles. Under these circumstances the 



