As it swiftly glides up the glass, we see that it has an oblong body
of a pellucid white hue, curiously beset with finger-like appendages.
There is a row of some half-dozen or so fringing the front of the head;
and down a line on each side of the body, margining the mantle, there
is a row of larger ones, and all these are tipped with the richest
orange colour. Just behind the frontal points there are two club-shaped
organs, which start up out of holes, the sides of which form sheaths
for them, into which they can be withdrawn at the will of the animal.
These organs carry a number of narrow plates set parallel to each
other, diagonally pointing backwards and downwards. Doubtless, this
structure is intended to augment the sensitive powers of these curious
organs, which are understood to be the tentacles.
Then, in the middle line of the back, but placed a little nearer the
tail than the head, there is an orifice, which is the vent; remarkable
because the breathing organs are arranged partly around it. There
are three tiny leaves cut like the fronds of a fern, which stand up
over the orifice, and are endowed with the power of absorbing for the
purposes of respiration the oxygen of the air commingled in the water.
But here is an animal which possesses all these peculiarities of
structure, displayed on a much larger scale. It is a fine specimen
of the Sea Lemon,[17] which we oftener find clinging to the sides
of perpendicular rocks, or beneath projecting ledges, than on the
undersides of stones. This fellow is two and a half inches long, and
an inch and a quarter or more broad; but I have met with individuals
much larger than he. Its back is rounded, and its outline generally
reminds one of the half of a lemon cut longitudinally. The resemblance
is heightened, too, by the round warts with which the whole surface is
studded, and by the colour, a yellow more or less pure, often, however,
clouded, as in this instance, with purple, by which its beauty is much
enhanced.
[Illustration: