The lecture given by Dr Yasumasu should be considered from two points of view, namely its significance in the field of developmental biology and his own personal history as a developmental biologist.

In 1908 Otto Warburg published a paper entitled ‘Beobachtungen üeber die Oxydationsprozesse im Seeigelei’ (Warburg, 1908). This is one of his earliest works, where he measured respiration of eggs with Winkler's method not with his manometer. This was the first paper describing the fact that the respiration in unfertilised eggs was considerably lower than that in fertilised ones. Many researchers confirmed his experiments and extended them. Borei (1948) measured oxygen consumption of oocytes and unfertilised and fertilised eggs and compared his results with those of other researchers. He observed that the respiration of eggs declined after they were removed from the ovary and placed into seawater and that it increased at fertilisation. He observed an exponential increase in respiration of fertilised eggs or embryos from the cleavage stage to the hatching blastula. He also observed an initial burst of respiration but failed to record it exactly. Ohnishi & Sugiyama (1963) measured the initial burst of respiration quantitatively with the oxygen electrode method. Thus, respiration of sea urchin eggs and early embryos was divided into three phases: respiration of unfertilised eggs, the initial burst of respiration at fertilisation and the respiration of fertilised eggs. The respiration of fertilised eggs increased exponentially with progression of development until hatching.