AXIAL FILAMENT OF SILICIOUS SPONGE SPICULES, ITS ORGANIC COMPONENTS AND SYNTHESIS

1. A substantial portion of the axial filament of the spicules of silicious sponges is protein. 2. The axial filament protein lacks the hydroxylated amino acids that are characteristically abundant in collagen. 3. It is feasible to follow the course of silicious deposition in spicules using C¹⁴ or H³ in protein precursors.