The metabolism of the eggs of Psammechinus miliaris during the fertilization reaction

Most of the work on the effect of fertilization on the metabolism of seaurchin eggs has been concerned with the average rate of O 2 consumption before and after activation. Although observations of this type are of interest, the changes which take place during the actual fertilization of the eggs are more indicative of the mechanisms responsible for the initiation of development. Technical difficulties have impeded experiments of this latter type. Early workers (Warburg 1915) found it necessary to fertilize the eggs before the beginning of the experiment, or, after measuring the O 2 consumption of unfertilized eggs, to open the manometer vessels to effect insemination. The former method precludes any measurements during the fertilization reaction, and the latter involves a period of manipulation and consequent re-equilibration which exceeds the duration of the fertilization reaction. When, therefore, it is stated that the O 2 consumption rate increases upon fertilization or parthenogenetic activation by some 200-400%, what is usually implied is that the O 2 consumption rate measured over a considerable period of time after insemination is some 200-400% more than the rate for a similar period of time before insemination. Shearer (1922) was the first to realize the importance of measurements immediately after insemination; 1 min. After insemination he observed an increase in O 2 consumption which was not maintained at the original high level. We have been unable to confirm Shearer’s results when using a similar method (see fig. 2). In recent years further attempts have been made (e. g. Runnström 1933 b ; Brook, Druckrey and Herken 1938) to make measurements immediately after fertilization by having the sperm inside the manometer vessel before fertilization but separate from the eggs; at a given moment sperm and eggs are mixed; but in these condition, the shortest time interval measured after insemination was 10 min. (Runnström), by which time the initial phase of the fertilization reaction is over.