378 THE COMMON PURPLE, OR PURPURA. 



more muddy parts of the coast, and prefer deep to shallow water. None of the Harp- 

 shells possess the operculum. 



The colour of the Imperial Ha.rp is pale chestnut and white, with a dash of yellov 

 arranged in tolerably regular and slightly spiral bands. 



THE smaller figure on the right-hand, having the animal attached, is the LITTLE HAEF- 

 SHELL, a darker species, and one that seldom attains a greater length than an inch and a 

 half. This figure is given for the purpose of showing the peculiar foot, which is very 

 large, broad, and leaf-shaped, and, as will be seen by reference to the illustration, has a 

 deep fissure just behind the tentacles, nearly cutting the organ asunder. It is said that, 

 when the animal is irritated, the fissure becomes widely expanded. Some writers say 

 that, if the animal is very much terrified, it withdraws itself into its home with such 

 rapidity that the expanded front of the foot is unable to contract sufficiently, so that the 

 fissure is caught against the sharp front edge of the shell, and thus undergoes involuntary 

 amputation. 



The general colours are tolerably similar . throughout the Harps, but each species 

 always preserves its peculiar individuality. One species, for example, has the spaces 

 between the ridges pencilled in elaborate wavy markings of chocolate on white, and the 

 ribs themselves barred at regular intervals by lines of deep brown ; while another, known 

 by the name of VENTEICOSE HARP (Harpa ventricosd), has the spaces filled with a 

 succession of arches, one within the other, and of a rich brown colour. 



A VEEY common shell may often be found on the seashore, looking like a small whelk 

 with a smooth whitish shell, boldly banded with reddish brown. This is the COMMON 

 PUEPLE, or PUEPUEA (Purpura lopillus\ another member of this genus, and worthy of 

 notice as being one of the shells which furnish the celebrated Tyrian purple of the ancients. 

 This colour, which, by the way, contains so little blue as to be unlike the tint which we 

 now call by the name of purple, is evidently the analogue of the ink found in the sepia, 

 and is secreted in a little sac by the throat, containing only one small drop. 



For the very best dye this material was extracted carefully from the individual shells, 

 but for an inferior kind it was obtained by pounding a quantity of the Purpurse in a 

 mortar, and straining off the juice, which was thus mixed with the blood and general 

 moisture of the animals, and consequently of less value than the pure dye. So expensive 

 was the dye obtained by this latter process, that a pound of wool stained with it could not 

 be purchased under a sum equalling thirty pounds of present money. Any one can try 

 the experiment of dyeing a little strip of linen with the matter obtained from a single shell. 

 After breaking the shell carefully so as not to crush the inhabitant, the cell containing 

 the colouring matter will be seen lying across the head or neck of the animal, and can be 

 removed by opening the sac and taking up the yellowish white contents with a small 

 camel's-hair brush, or the point of a new quill-pen. When the linen is imbued with 

 this liquid and placed in the rays of the sun, it immediately begins to change its colour, 

 and passes through a series of tints with such rapidity that the eye can hardly follow 

 them, unless the slanting rays of the rising or setting sun are chosen for the purpose. 



Light green is the first tint, which soon deepens until the yellow is driven out by the 

 mysterious power of light, and the substance assumes a blue colour. After a while 

 another primary colour makes its appearance, and a gradually deepening red being diffused 

 through it, the blue changes to rich purple. Even the blue, however, has a comparatively 

 feeble hold, for if the empurpled linen be well washed with soap and water, and again 

 exposed to the sun's rays, the blue gradually fades before the increasing red, and a deepish 

 crimson will be the ultimate result. Thus, we have the curious phenomenon of a semi- 

 liquid, almost destitute of colour while shielded from light, assuming in regular succession 

 the three primary colours, first mixed so as to form the secondary tints, and gradually 

 separating and retiring before the superior power of their successors. 



The eggs of the Purpura may often be found adhering to stones, shells, or even to each 

 other, by means of little footstalks, which give the object a singular resemblance to an 

 egg-cup with the egg placed in it. 



