86 COLOUR AND FORMATION
Mrs. Ashton, " are brought from the Red Sea and the East Indies. Those which are found in the West Indies are less brilliant; and the shells of colder regions possess still less lustre and variety of colours: so that this difference may very reasonably be attributed, in some measure, to solar heat: perhaps, too, those seas in which the most brilliant shells are found, may furnish a greater supply of nourishment to the animals which inhabit them, and thus cause their shelly coverings to increase in size and beauty."
" Do you really mean, mamma," said Edward, u that shells grow?"
" Yes, my dear: naturalists tell us, that an infant shell-fish is covered with a testaceous coating, which is