The fecundity of these mollusca is immense. An _Eolis papillosa_ of
moderate size in one of my aquaria, deposited successively nine strings
of spawn between March 20th and May 24th. The strings were exactly
alike in length and arrangement; each comprised about 105 convolutions,
and each convolution 200 eggs, while each egg contained on an average
two embryos. Thus the astonishing number of 378,000 embryos proceeded
from this one animal in about two months.
Step by step we have crept along the beach, turning stones as we went,
till we are come to the great masses of sandstone rock. Here are the
Purples[21] by hundreds, with their strong massive shells, some of them
pure white, which, however, becomes dingy with age, some banded with
brown, and some, especially the young and half-grown ones, painted
with a dull but soft purplish hue. The older specimens have the inner
surface of the lip tinged with a rich rosy purple. This tint on the
shell we may receive as the advertisement of the colorific property
that resides within, a sort of sign-board to tell us that this is the
“genuine” purple-shell. And there is little doubt that it is one of
those enumerated by Pliny, as used by the ancients for obtaining the
renowned dye of Tyre: though the principal, and that which yielded the
richest hue, was probably the _Murex trunculus_, a common Mediterranean
shell, which does not extend to our shores.
[Illustration: