“…A similar discrepancy exists between the results of various cytogenetic studies dealing with other chemical agents, viz. the folic acid antagonists (Ryan et al, 1965;Hampel et al, 1966;Krogh Jensen, 1967) and lysergic acid diethylamide (Cohen et al, 1967;Irwin and Egozcue, 1967;Loughman et al, 1967;Bender and Sankar, 1968;Nielsen et al, 1968) and some viruses, viz. morbilli (Nichols et al, 1962;Tanzer et al, 1963;Aula, 1965;Gripenberg, 1965), and rubella viruses (Mellman et al, 1965;Nusbacher et al, 1967).…”