46 MOLEUSCA. 
same property. This liquor must not be con- 
founded with that which constitutes the purple dye 
of Murex, Purpura, &c. already mentioned, for it 
is so volatile as to be unsuitable for the purposes of 
APLYSIA. 
dyeing. According to Cuvier, the secretion in dry- 
ing assumes the beautiful deep hue of the sweet Sca- 
bious, and remains unaltered by long exposure to 
the air. Nitric acid, in small quantity, heightened 
the tint, but a larger dose changed it to a dirty. 
orange colour, while potash turned it to a dingy 
vinous grey. Both the acid and the alkali preci- 
pitated many white 
flakes from the fluid. 
The purple tintis readily 
transferred to spirit when 
the animal is immersed 
in 1t; the tincture retains 
this colour for awhile, 
but at length becomes 
PLANORBIS CORNEUS. of a deep clear red, 
like that of port wine. 
A very common shell in ponds and ditches, 
(Planorbis corneus,) coiled up like a ram’s horn, is 
