ORCHELLA. 221 



species. Pliny alludes to it under the name oi fucus mari- 

 nus, but he also applied the term fucus to the alkanet or 

 red-herb used in dyeing, and from which the rouge, with 

 which " vetulee vitia corporis fuco occulunt," was made. 

 He applies the term fucus also to the juice of the purple- 

 fisk, a gasteropodous mollusc, of the genus Murex, from 

 which the ancients are said to have made the beautiful 

 Tyrian purple. In his ( Dictionnaire Classique d'Histoire 

 NaturehV Bory de St. Vincent gives his opinion that the 

 purple dye of the ancients was prepared from the rock- 

 lichen (Roccella), and not from Murex ; as both are found 

 upon or near the sea-shore there is some probability of its 

 truth. It would be an interesting investigation, to ascer- 

 tain whether the purple secretions of many molluscs be not 

 derived from the vegetable food they gather from the shore ; 

 there is one point however which almost prevents the 

 supposition that they feed upon the Roccella, because it 

 grows upon the dry rocks; but it is not impossible that 

 some of the marine Alga and Fucoidea may yield the same 

 colouring principles. Should this be the case, Bory de St. 

 Vincent may be right, and we shall not have the interesting 

 legend destroyed which describes the discovery of the Tyrian 

 purple. This legend states that Hercules made a journey 



