Se ee eee ee a a 
Royal Society. 293 
PROCEEDINGS OF LEARNED SOCIETIES. 
ROYAL SOCIETY. 
Communication received since the end of the Session (June 21, 1860). 
‘‘ Natural History of the Purple of the Ancients.” By M. Lacaze 
Duthiers, Professor of Zoology in the Faculty of Sciences of Lille. 
The purple dye so esteemed by the ancients has by turns excited 
the curiosity of naturalists and of historians. The number of 
memoirs upon the subject is considerable, and they are to be found 
in almost all tongues. However, in all these works, remarkable in 
many respects, and which cannot be analysed in this short notice, 
three deficiencies are to be noted regarding matters of very great 
moment in the history of this substance. 
What are, Ist, the producing organs? 2ndly, the nature? 3rdly, 
the natural primitive colour of the dye? It is difficult to give any 
answer to these three questions by means of the facts contained in 
existing memoirs. It is for the purpose of replying to them that I 
have undertaken the investigation, whose chief results I have the 
honour now to lay before the scientific world. 
The two genera Murex and Purpura have yielded the species 
observed. In very distant localities, as at Mahon in Minorca, Murex 
brandaris, M. trunculus, and Purpura hemastoma have furnished 
results which observations conducted at Boulogne on Purpura la- 
pillus, at Pornic (Vendée) on the same species and Murewx erinaceus, 
and at La Rochelle and L’ Ile de Rhé, have confirmed. At Marseilles, 
Murex brandaris has yielded precisely similar results; and this 
concordance of all the observations permits me to offer them with 
much confidence. 
What is the organ which produces the dye? 
The analogy which some chemists imagine they have found 
between the colour of alloxan or of murexide and the purple of the 
Mollusca, has led them to misconceive the nature of the organ which 
produces the colouring matter. It is indubitable that uric acid 
treated with nitric acid gives a beautiful reddish purple colour when 
the residue is exposed to ammoniacal vapour; and this reaction 
furnishes a means of detecting the renal organ in mollusks. But 
from this circumstance no one could be justified in coucluding that 
the purple dye was either the secretion of the kidney or the result of 
a modification of the urine. 
Careful dissection of the purpuriferous mollusca proves that the 
purple dye is secreted by a very limited portion of the mantle, which 
ean in no way be confounded with the true renal organ, as which 
the organ of Bojanus is now generally regarded ; the position and 
the structure of the purpuriferous organ are indeed totally different 
from those of the kidney. 
Small in extent, this part occupies very nearly the space bounded 
by the branchize and the rectum, beyond whose extremities it 
hardly extends anteriorly, while posteriorly it, at most, reaches the 
