And from the gut downward extend black and
rough formations, in close connexion, something like the formations in
the tortoise, only not so black. Marine snails, also, have these
formations, and the white ones, only that the formations are smaller
in the smaller species.
The non-spiral univalves and bivalves are in some respect
similar in construction, and in some respects dissimilar, to the
spiral testaceans. They all have a head and horns, and a mouth, and
the organ resembling a tongue; but these organs, in the smaller
species, are indiscernible owing to the minuteness of these animals,
and some are indiscernible even in the larger species when dead, or
when at rest and motionless. They all have the mecon, or poppy, but
not all in the same place, nor of equal size, nor similarly open to
observation; thus, the limpets have this organ deep down in the bottom
of the shell, and the bivalves at the hinge connecting the two valves.
They also have in all cases the hairy growths or beards, in a circular
form, as in the scallops. And, with regard to the so-called 'egg',
in those that have it, when they have it, it is situated in one of the
semi-circles of the periphery, as is the case with the white formation
in the snail; for this white formation in the snail corresponds to the
so-called egg of which we are speaking.
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