“…2 Seven species , including T. rivale which has very little heterochromatin, are known to possess supernumeraries. This does not support the suggestion of Darlington and Shaw (1959) that the presence of H-segments and of supernumeraries is positively correlated. Their observation that supernumeraries are absent from T. stylosum but present in 5 other species from the same area, could equally well be correlated with the fact that the latter, unlike T. stylosum, were collected at the edge of the species range (map, Fig.…”