one possible mechanism behind nondisjunction is a malfunctioning spindle . 
 a defect or lack of spindle is a criterion for c - mitosis . in chemical mutagenesis research 
 the c - mitotic effect is a well known cytological phenomemon , which can be induced by many different compounds . 
 pioneer work was performed during the 1940 's by ostergren and levan , and their results and conclusions are briefly discussed . 
 since colchicine can induce c - mitosis and c - meiosis , by definition , and nondisjunction , a correlation between these phenomena is logical . 
 the general importance of the spindle protein tubulin is considered and some new data from the cell biology literature on spindle formation and function as well as chromosome structure are briefly summarized . 
 this knowledge can be used to correlate cytological and biochemical parameters among which c - mitosis and changes in sulfhydryl group metabolism after chemical treatment are the most obvious ones.imagesfigure 3 .