384 MURICIDiE. 



The eyes are black and conspicuous. The head is kmate ; 

 the tentacula thickened for more than half their lengths, 

 to carrvthe eves on the extremities of their external bulo- 

 ings, or, in more strict language, combined ommato})hori. 

 The mantle is yellowish, with slightly scalloped margins : 

 the edges of its siphonal fold are turned in. The foot is 

 oblong, and when at rest has its anterior part contracted 

 and unfolded. The broad and angular operculum is of a 

 bright tawny coloui-, and overlaps the membranous rounded 

 short operculigerous lobe. The receptacle of the creamy 

 secretion which furnishes the purple dye lies behind the 

 animaPs head, and Montagu observes that it appears 

 whiter than the rest of the animal. The purple hue is 

 not developed until after exposure to air and light, when 

 it passes through successive phases of yellow, green, and 

 blue before exhibiting its royal tint. It appears to be 

 easily fixed, and to become more brilliant by use. It 

 was formerly employed for dyeing fine linen in Ireland 

 (in 1684), but is not applied to any such purpose 

 at present. Reaumur found that its egg-vesicles yielded 

 the dye with less trouble than the parent Mollusk. 



These egg-vesicles are little oblong urn-shaped cups, of 

 tough though membranous texture, and yellowish colour 

 tinged often with pink. They are shortly pedunculate and 

 stand erect in considerable numbers, rising from a common 

 membrane which is attached to the surface of rocks or 

 stones, or sometimes on the parent shells themselves. 

 Each contains many embryo Purpura. Mr. Peach has 

 bred them, and has observed that they change form as the 

 included young ones ripen, the apex of the cup becoming- 

 thinner and more convex. He found that so long a time 

 as four months elapsed before the vesicle opened, and then 

 the included whelklings did not quit their cradle all at 



