It has recently been ascertained that the coloration of certain sponges is due to the interaction of an oxydizing ferment, tyrosinase, upon certain colourless chromogenic substances.
Furth and Hugo Schneider showed that a tyrosinase could be obtained from the blood of certain insects, and, acting upon a chromogen present in the blood, converted it into a pigmentary substance of melanin-like nature.
Hans Przibram also extracted a tyrosinase ' from the ink-sac of Sepia, and, causing it to act upon a watery solution of tyrosin, obtained a black pigment.
Bertrand have shown that certain fungi, the tissues of which, when exposed, to the air by injury, become immediately coloured, do so owing to the action of tyrosinase upon one or more chromogenous substances present in the plant.
Whether albinoes carry the tyrosinase or other ferment, or whether they carry the chromogen or chromogens, is not yet settled.