“…Temperature effects on chromosome con traction have been described by Matsuura (1935Matsuura ( , 1937, Straub (1937), Huskins and Wilson (1938), Wilson and Huskin (1939), Barber (1940), Darlington and LaCour (1940), Swanson (1942Swanson ( , 1943, Wilson and Boothroyd (1944), Jain (1957) and Rees (1958). Genotypic control of chromosome length has also been known for many years (Lesley and Frost 1927, Lamm 1936, Upcott 1937, Swanson 1942, 1943, Burnham 1946). Differences at the cell level are due mainly to differences in stage advancement, differences in treatment during slide preparation which are not found at the slide level and to internal differences in cellular environment which have the same general pattern of distribution in all anthers (for example, differences in position of the various chromosomes with respect to each other might conceivably influence contrac tion rate).…”