Spindle and Cytoplasm 93 



cocioHs reversion" Iroin c-metaphase or earlier arrested stages as well 

 as a recovery in due course of time, often true for animals''*^' ^^- -^- "•'■ 

 78. !ti,s.>. 1)^ ,^o[ limited to them, creates a restitution nucleus or 

 daughter nuclei with diploid luimhcrs of chromosomes (centro- 

 meres) , because in these cases a c-anaphasc does not obtain, under 

 conditions of rei'ersiou or recovery, from an arrested stage. However, 

 doubling of chromosomes can and does take place among animal cells. 

 51, 76, 86, 11. 3, 4, 2, 83. 22. 74. 65. 81. 48 Altliough this piocess of dupUcatiou 

 is more common to ])Iants treated with colchicine, neither situation 

 should be regarded as typical for one grouj) or the other. Such gen- 

 eralizations lead to false conclusions. 



rhree statements concisely express the primary concepts: (1) 

 c-mitosis creates a jjolyploid restitution nucleus via c-metaphase-c-ana- 

 phase-c-telophase })rocesses; (2) c-mitosis by precocious reversion from 

 c-metaphase, or earlier arrested stage, may with exceptions, lead to a 

 nonpolyploid restitution nucleus; (3) c-mitosis may after due time re- 

 cover from the arrested stage and dexcloj) regular anaphase, instead 

 of the c-anaphase, thus leading to diploid daughter nuclei. 



Greater than all these remarkable features is the underlying bio- 

 logical principle of reversibility. When the cell, in contact with the 

 drug for a given time, is removed from the influence of colchicine, 

 either by actual transfer or by allowing dissipation of chemical dining 

 a recovery period, the characteristics of reversibility come into locus. •^•'' 



Cells treated \vith optimal dosages that induce a c-mitosis creat- 

 ing the polyploid nucleus, recover so that a normal mitosis may fol- 

 low with a fully finictional bipolar spindle. That is, a restitution 

 nucleus can regenerate a bipolar sj)indle after the effects of colchi- 

 cine are remo\ed.-'^ 



Resieneration amony- the restitution cells is peinianent, and cells 

 develop spindle mechanisms in each succeeding division with meta- 

 phase, anaphase, telophase, and, of course, the doubled number of 

 chromosomes. This new divisional process continues thus, as long 

 as the cell lineage retains jjower to divide. Polyploidy is thereby main- 

 tained and continued without attending cvtogenetic changes, except 

 for those effects related to an increasing numlxr of chromosomes ]jer 

 cell.-55 No one has demonstrated by careful cytogenetic methods that 

 colchicine at optimal doses for a c-mitosis leading to polyploidy, also 

 increases the frequencies of mutations or chromosomal changes.-'-'' '■'- 

 Caution at this jjoint is advised because miuations and chromosomal 

 changes mav occur inde])endenily of colchicine but simultanecnish 

 with a treatment.-'-' 



1 he capacity of the cell to recover after a treainunt. to legenerate 

 a bipolar spindle following a c-mitosis, to reverse the ina(ti\aiing 

 effects ol colchicine upon spindle: these are, in oin- opinion, the most 



