The colour of the dye is scarcely what we understand by the term "purple," _i.e._ a mixture of blue and red. It has but very little blue in it, and has been compared by the ancients to the colour of newly-clotted blood. It is obtained from several Shell Fish belonging to the great Whelk family, the chief of which is the _Murex brandaris_. The shell is shaped something like that of a whelk, but is very smooth and porcelain-like, and is generally white, ornamented with several coloured bands. It is, however, one of the most variable of shells, differing not only in colour but in form. It always inhabits the belt of the shore between tide-marks, and preys upon other Molluscs, such as the mussel and periwinkle, literally licking them to pieces with its long riband tongue. This tongue is beset with rows of hooked teeth, exactly like the shark-tooth weapons of the Samoan and Mangaian Islanders, and with it the creature is enabled to bore through the shells of mussels and similar Molluscs, and to eat the enclosed animal. It is very destructive to periwinkles, thrusting its tongue through the mouth of the shell, piercing easily the operculum by which the entrance is closed, and gradually scooping out the unfortunate inmate. Even the bivalves, which can shut themselves up between two shells, fare no better, the tongue of the Dog-Whelk rasping a hole in the hard shell in eight-and-forty hours. In order to procure the animal, the shell must be broken with a sharp blow of a small hammer, and the receptacle of the colouring matter can then be seen behind the head, and recognised by its lighter hue. When it is opened, a creamy sort of matter exudes. It is yellowish, and gives no promise of its future richness of hue. There is only one drop of this matter in each animal, and it is about sufficient in quantity to stain a piece of linen the size of a dime. The best mode of seeing the full beauty of the purple is to take a number of the Molluscs, and to stain as large a surface as possible. The piece of linen should then be exposed to the rays of the sun, when it will go through a most curious series of colours. The yellow begins to turn green, and, after a while, the stained portions of the linen will be entirely green, the yellow having been vanquished by the blue. By degrees the blue predominates more and more over the yellow, until the linen is no more green, but blue. Then, just as the yellow yielded to the blue, the blue yields to red, and becomes first violet, then purple, and lastly assumes the blood-red hue of royalty. The colour is very permanent, and, instead of fading by time, seems rather to brighten.