ON GASTEROPODA. 359 
greater number and the largest come from the warmer lati- 
tudes, and more especially from the Austral seas. But with- 
out considering this genus more minutely, we shall seize the 
present opportunity of treating concerning the purple of the 
ancients. 
The words zoo¢tea, or purpura, were indifferently em- 
ployed by the Greeks and Romans, to designate the colour 
itself, and the animal which furnished it. Aristotle is the 
first writer who has spoken of the purpura. He tells us that 
“‘ with the exception of the head, all its other parts are con- 
tained in the shell; it is provided with a very firm proboscis, 
by means of which it pierces the testa of the animal on which 
it feeds. In the turbinated part of the shell lie the stomach, 
liver, and intestines; between the neck and the liver is the 
organ which furnishes the colouring matter; it has the form 
of a vein. The substance which fills the rest of the interval 
resembles alum.” Here it is probable that Aristotle alludes 
to the cretaceous matter frequently found in the rectum of 
many of the mollusca. He continues: 
“The purpure move but little; they remain concealed 
during the great heats of the dog-days. Fresh-water is posi- 
tively injurious to them; but they can live as long as fifty 
days out of water altogether. They can perceive. their 
prey from a very great distance. ‘They assemble in spring in 
the same place, and there make what is named their wax, 
which is a production resembling a cake of wax, except that 
it is not smooth, or rather a multitude of white pease-cods 
joined together; no aperture is ever perceived in it. When 
the purpurz, like the other testacea, commence to form this 
production, they produce a gluey mucosity, which serves to 
connect these sorts of pods. It is in this united mass that 
the young purpure are born, and that they are found attached, 
sometimes as yet imperfectly formed, to the shells of the old 
ones, when the latter are fished up. If the purpure be taken 
