428 
THE OCEAN WORLD. 
strated that the organ which, secretes it is found on the lower surfed 
of the mantle, between the intestines and the respiratory organs, wh® 1 ® 
it forms a sort of fascia, or small band. The colouring matter, as ^ 
is extracted from the animal, is yellowish; exposed to the light, 
becomes golden yellow, then green, taking finally a fine violet ti» t- 
While these transformations are in progress a peculiarly pung e0 
odour is disengaged, which strongly reminds one of that of assafffl^*' 
That portion of the matter which lias not passed into the violet tint n 
soluble in water ; when it has taken that tint it becomes insoluble 
The appearance of the colour seems provoked rather by the influent 
of the sun’s rays than by the action of the air. The matter attain 8 
its final colour, in short, in proportion to the power of the sun 
rays. 
It is a question, how far the colour evolved under the solar i' a J s 
remains indelible. It is known that the contrary is the case with t 
colouring matter of the cochineal insect, which changes very qn 10 * •' 
when exposed to the sun. It is probably the remarkable resists’ 1 * L ' 
it opposes to the rays of the sun which recommended it to 
ancients. The patricians of Eome, and the rich citizens of Gt eeC0 
and Asia Minor, loved 1° 
watch the magical refl eC 
tions of the sun on 1 6 
glorious colour which 01 
namented their mantle 8, 
to on 1 ' 
But to return 
humble shells. Purp^ r 
lapillus (Fig. 268) lS * 
thick shell, oval acute, ffl 
conical spiral, generally 
a faded or yellowish wbi* 8 ' 
i 
Fig. 268. Purpura la- 
pilltts (Llnnteus). 
Fig. 261 ). Purpura patula 
(Lirmifus). 
zoned with brown, a ” 
more or less spotted. 
Purpura patula (Fj^ 
269) is a species so common in the Mediterranean that Cohn®' 
thought it was from this species in particular that the Romans obtai Jie 
their fine colour. 
Purpura consul (Fig. 270) is one of the largest shells, and ° 
fine thick white colour. 
