AbstractThe water exchange has been measured in oocytes ofsiredon mexicanumandrana temporaria, and in unfertilized eggs and early gastrulae of the former species, by recording the D2OH2O exchange with the cartesian diver balance.In oocytes, where no diffusion barrier to water is demonstrable, the temperature coefficient Q10for the exchange of water is about 1.3–1.4, corresponding to that of free diffusion. in unfertilized eggs, and in early gastrulae the exchange is considerably slowed down, indicating that a surface membrane to some extent limits the rate of exchange. at the same time the Q10value is increased, lying in the range 2.3–3.8. since it is most likely that the exchange even in this case occurs by diffusion, but through membrane pores, it is concluded that the area available for diffusion (pore size or number, or both) increases with temper
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