Nucleus and Chromosomes 



41 



is a complete lack oi the usual equatorial metaphase orientation, 

 hence the epithet uuorwntcd (Fig. 2.1C. 2AD, and 2.8^). 



The exploded nietaphases were described from cells of mice 

 treated with strong doses of sodium cacodylatc."" Therefore, a re- 

 appearance with colchicine tended to call attention to similarities be- 

 tween the two substances.-^-^ 



Among regenerating liver cells follo\\ing hepatectomy, the ex- 

 ploded metaphase is very characteristic (Fig. 2.8^) . 1 he investi- 



Fig. 2.6 — Cell of Allium root tip with an excessive number of chromosomes. FixecJ 

 after treatment for 208 hours, with 0.05 per cent colchicine in nutrient solution. The 

 cells are beginning recovery; multiple star metaphases are present. Later cell plates 

 form between the groups reducing one large cell to a number of smaller cells. Cf. Chap- 

 ter 3. (After Mangenot) 



gators^-- ^^ described the unusual arrangement as though the in- 

 dividual chromosomes "repulsed one another." These widely scat- 

 tered chromosomes in a single cell were equally impressive from other 

 animals, the tissue cultures, and special cases, e.g., Siyedoti.-'^ Triton.'^ 

 Tritiiyiis,''' and Orlhoptera.^' With plants. Allium root tips have 

 been a favorite source for these types, but pollen tubes show unusual 

 scattering of the c-pairs through the length of a single tube (Fig. 

 2AD) . 



A specific concentration (2.5 X 1^^'*^ ^^^) applied at late prophase 

 created the exploded metaphase in grasshopper neuroblastic cells. 

 Similarly, critical dose-time reqtiirements were necessary to jjroduce 

 an arrested exploded metaphase in the regenerating cells of liver 



