1. The principal inorganic constituents of the unfertilized egg of Paracentrotus lividus have been analysed by chemical methods. The results of the analyses, in millimoles per kg. of water in the eggs (dry weight of eggs, 24%; density, 1.09), were:
The figures in brackets are the concentrations of the same substances in Roscoff sea water, chlorinity 19.37‰ in the same units.
2. The total phosphorus content of the eggs was about 2 mg./ml. eggs, somewhat over half of this being acid-soluble phosphorus.