Nuc/eus and Chromosomes 51 



it does not prevent chromosomal formation.' But colchicine does 

 one thing important at this stage; it desynchronizes the separation of 

 the chromosomes.^-*' ^^- ~^' ^*'- -^ Or we may say the coordinated pro- 

 cesses of anaphasic separation of all chromosomes at one particular 

 moment are very badly upset. 



Colchicine does not inhibit the uncoiling or the stage of katachro- 

 Nuisis:-'-' the return to interphase. The drug in certain concentration 

 does slow down the uncoiling process in Tradescantia since it takes 

 60 minutes for uncoiling with 0.05 per cent colchicine and 77 minutes 

 in 0.1 per cent contrasted with 35 minutes among untreated cells. 

 There is one other relation of interest: The ratio of time for chromo- 

 somal formation, anachroinasis, to chromosome uncoiling, hntachro- 

 masis. is about 2:1 in regular mitosis. Colchicine-treated mitoses main- 

 tain this 2:1 ratio, i.e., 121:60 in colchicine and 97:35 for untreated 

 cells. The significance of these corresponding figures is not under- 

 stood. 



The loss of chromatin, dcspiralization, and vesiculating stages^-* 

 in the presence of colchicine are much the same as in normal plant 

 cells. A solid chromosome becomes perforated, and two twisted coils 

 appear. The chromosome is reduced to a zigzag thread. There is a 

 fusion of chromosomes that lie close by and the final stages appear 

 as a reticulated network with nucleoli'^ and a membrane surrounding 

 the chromatin. Whether the change begins (1) from prophase, or (2) 

 from arrested metaphase, or (3) through c-anaphase, the general 

 dcspiralization, sometimes called unraveling, dechromatization, or 

 katachromasis, is similar (cf. Chapter 3) .^-i- ^c 93. m. i 



A full c-mitosis implies tliat the c-pairs of chromosomes "fall 

 apart" like "pairs of skis"'- '- in the cytoplasm (cf. Chapter 3; 

 Fig. 2.10). Allitini root tips (Fig. 2.10D), particularly, demonstrate 

 this stage except when stickiness holds them together. Thus the c- 

 anaphase can be observed without question.-^^, g5, i, 79 Such separation 

 is evidence that the restitution nucleus shall carry the tetraploid ntim- 

 ber of centromeres. 



Desynchronization is most easily observed if the chromosomes can 

 be compared at a given moment. For example. Figure 3.7 shows a c- 

 anaphase pair at the bottom, whereas above, c-pairs are clearly in X's 

 and held together." This has been shown over and over, from plants 

 and animal's, at arrested metaphase.-^*'- -^**' ^=5 within one set, single 

 chromosomes, and others in c-pairs, have been noticed to revert^^ to 

 interphase. 



C-anaphase is more distinct in some plants, but the distinction is 

 by no means valid for differentiating animals from plants.^"?, s^. 3, 2. 1. 70, 

 5« Tetraploid restitution nuclei have been observed for many kinds of 

 animal cells treated with colchicine. 



