Manufacturer and Builder 11, 1890
A correspndent, referring to our answer to Query 4114 (page 264 of our issue dated November, 1888), covering the subject named in the above caption, encloses the following extracts from the French Journal Science en Famille: "The shell of the crab and lobster owes its bluish-gray color to the superposition of two pigments, or coloring matters, which have been isolated — a red pigment and blue one. As long as these two pigments exist simultaneously, the crustaorans remain gray. But the blue pigment is very fugitive, and sometimes, under the influence of a disease, it is destroyed, and crabs are found with portions of their shell more or less reddish. When the crustaceans are immersed in boiling water, the blue pigment is entirely destroyed, and the red pigment, which is very stable, appears alone in all its brilliancy." To which we may cold, that the foregoing statement affords a very plausible explanation of this curious phenomenon, and the only attempt at an explanation that we have thus far met.
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