Elemental composition of the perivitelline fluid in early Drosophila embryos.

Samples of the perivitelline fluid in the polar pockets of preblastoderm Drosophila embryos were analyzed with an electron microprobe, and the results compared with analyses of adult hemolymph. The concentrations of sodium, magnesium, calcium, chlorine, and phosphorus are about the same in these two fluids; but potassium and sulfur are three to four times higher in perivitelline fluid. Moreover, the concentrations of these elements in the anterior and posterior pockets of the same embryos were compared. The former five elements seem to be about 10% more concentrated in the anterior pocket; but the latter two show no significant difference between pockets.