Perhaps you may be more interested in the development of the
Dog-winkle. Under the ledges of rocks we find in abundance groups of
little yellow bodies, resembling ninepins in shape, set on their ends
in close contact with each other, and varying in numbers from three or
four to a hundred or upwards in a group. Some of them are tinged with
purple at the tips; and while sometimes you find them closed, and full
of a yellow creamy substance, at others they are open at the top, and
empty.
These are the egg-capsules of this mollusk, and some very unusual
circumstances connected with the birth of the progeny, and their
development within these cases, have been discovered by Dr.
Carpenter.[23] Each capsule contains 500 or 600 globules that cannot
be distinguished from each other at first; but only twelve to thirty
of these are developed into young animals, though their united bulk
ultimately equals that of the whole mass. The greater number of these
globules are not real eggs, but only “yolk-spherules,” destined to
afford nutriment to the true embryos, which greedily swallow them,
after certain changes have taken place, and increase rapidly in bulk.
It is curious, however, that they do not advance in development during
this absorption of nutriment, but are, so to speak, arrested until a
great augmentation of size is thus attained; then they quickly acquire
the form of little free-swimming nautiloids, closely like those of the
Doris and Eolis, a form which indeed is common to the early stages
of all the known higher mollusca, however various may be their adult
conditions.