“…On this theory synchronization would be expected whatever the source of 'shock' and whatever the phase of the growth cycle of the culture treated, and it is, therefore, not surprising that synchronization has been produced by temperature 'shock' (Hotchkiss, 1954;Lark & Maalrae, 1954;Szybalski & Hunter-Szybalska, 1955), by nutritional 'shock' (Barner & Cohen, 1956 ;Yanagita, 1954;Burns, 1959) and in Chlorella by light 'shock' (Tamiya et al, 1953). It follows that if size is related to age then inocula of cells of similar size should yield synchronously developing populations ; hence the great utility of the filtration technique of Maruyama & Yanagita (1956).…”