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In contrast, fluorescent lysozyme (FLy), a basic protein, is observed to remain within the nurse cells after injection. This is explained by the fact that the oocyte cytoplasm is about 10 mV more positive than that of the nurse cells. Reprinted by permission from Nature , Vol. 286, pp. 84-86. Copyright © 1980 Macmillan lournals Limited. Although we have limited our discussion of the role of ion currents in development to these two well-studied examples, it is probable that such currents as well as more transient electric fields associated with changes in membrane potentials will have general importance in influencing cellular differentiation and growth in the biological world.

Fresh spores do not germinate easily, but anyone of a number of treatments "shock" or activate them so that germination is facilitated. Aging for several weeks, sublethal heating, or exposure to low pH, sulfhydryl-containing compounds, or organic solvents such as dimethylformamide serve to activate the spore. Activation is required for fresh bacterial endospores, but not for germination of bacterial or eukaryotic conidiospores or spores derived from fruiting bodies. Numerous agents have been found to initiate germination of activated endospores, and these are to some extent species-specific.

In contrast, if cells were not aligned by light, no current was driven through the tube (B). Current patterns around the cells that were inferred from these experiments are shown by the curved arrows. (Adapted from L. Jaffe, Proc. Natl. Acad. Sci. 8. Use of a vibrating platinum electrode to measure current patterns around a developing Pelvetia egg. (A) Micrograph of the vibrating electrode (arrow shows the axis of vibration) near a Pelvetia egg 3 hr after fertilization. (B) St~ady current pattern inferred by making measurements with the probe at various position~ around the egg cell.