42 Colchicine 



(hepatectomized rats) .^i- ^'^ Supralethal doses did not induce maxi- 

 mum arrested metaphases or exploded metaphases. There is then an 

 optimum dose required for this type. Apparently this same rule 

 holds for pollen tubes, because maximum scattering throughout the 

 tube occurred only under given conditions of concentration and 

 favorable pollen tube growth. -^^ There are other cases bearing on 

 this point. 



Prophase-metaphase arrangements of chromosomes as an un- 

 oriented type are frequently observed (Fig. 2.2B) . The spleen of 

 Siredon yielded these types among the first colchicine-arrestcd mitoses 

 ever studied (Fig. 2.2) .-^- ^^ Perhaps a more logical descriptive term 

 would be arrested prophase, since the prophase orientation is main- 

 tained as the nuclear membrane disappears. No sign of spindle move- 

 ment is detected. The chromosomes may revert to the interphase 

 from a prophase-metaphase. During periods as long as five days after 

 injection, the prophase-metaphase appears in Siredoti (Fig. 2.9) . 

 Representative cases in animals arc noted for this type.^'^' ^- Follow- 

 ing anaphasic treatment the intermingling of two sets of chromosomes 

 leads to a similar prophase-metaphase grouping,-^-* so that treatment 

 at prophase or at anaphase might give this vnioriented association. ^^^ 



Ball metaphases^ are distinctly clumped types (Figs. 2.2, 2.5) . In 

 fact, the clumped c-mitosis observed in Spinacia,' Lepidiuni, and 

 Petroselimtni^''' are typically ball metaphases. A toxic action is un- 

 doubtedly responsible for the particular apparent fusion of un- 

 oriented chromosomes. The next step in progressive development is 

 either the degeneration after pycnosis or recovery to an intcrphasic 

 stage. Triton material was represented with more ball metaphases 

 than any other imoricnted type. Even though chromosomes appear 

 clumped, an individuality may be maintained as was pictured for 

 cells of mice by the lacnioid-acetic method applied to a ball meta- 

 phase.^^ Many of these mitoses undergo destruction eventually in 

 warm-blooded animals.''^ Lysis or degeneration after a ball metaphase 

 may account for the destruction noticed in Tiibifex.^^' ^^' ^^ 



Ball metaphases are regularly produced in pollen tube cultures 

 when the concentrations exceed .01 per cent in culturing media. -^^ 

 Clumping at the early stages followed by pycnosis and eventual lysis 

 forms the regular course taken by the ball metaphase in pollen tube 

 cells. Similar degeneration and settling of chromosomes in neuro- 

 blastic cells indicate destructive action as accompanying this particular 

 unoriented type. 



Much discussion has been directed to the distributed c-mitosis, a 

 type that can be clearly demonstrated in pollen tubes when the c- 

 pairs group into two clumps (Fig. 2 AD) . The chromosomes are 

 c-pairs, and separation may or may not be equal in number. The 



