Acid-soluble Pigments of Molluscan Shells

blue with nitrites (Schultz, 1931). This group does, however, behave as a consistent chromatographic series. A rather similar family of pigments occurs in several archaeogastropod shells, especially among the red Trochidae and Fissurellidae, though chromatograms of these forms could not be repeated to our satisfaction owing to shortage of material. In other forms related to the porphyrin-producing groups, such as Turbo and Halioti8, we have been able to confirm Krukenberg's (1883) finding of bilitrienes but bilitrienes and porphyrins do not appear to coexist. Mixed chromatography of Pinctada extracts with turboglaucobilin, with Halioti8 blue and with the products of an incomplete Gmelin reaction performed on biliverdin from bile, shows no evidence of correspondence between known and unknown pigments. The acid-soluble pigments of Pinctada have the following characteristics: they are indicators, changing to grey or greenish blue in alkaline solution; they are adsorbed from acid solution on talc in a consistent order, red falling lowest and violet highest upon the column; they are insoluble in organic solvents except acetone, ethanol and methanol, but they pass into amyl alcohol from acid solution on prolonged standing in a manner which resembles the behaviour of porphyrins, and strongly suggests esterification; they are nonfluorescent, and their visible absorption spectra are characteristic. A close phylogenetic relationship exists between these pigments and shell porphyrins. They are found in typical purplish or reddish colour schemes, which seem to occur most commonly in primitive or unspecialized forms.