The animal is one of the Sea-slugs, allied, not remotely, to the
_Doris_ and the lovely _Eolis_, which occupied our attention some time
ago. The order to which it belongs is, however, distinguished from them
by having the breathing organs covered. In our Sea-hare these take the
form of complicated leaflets, which are placed upon the middle of
the back, and are protected by a broad plate of shell, somewhat like
a watch-glass of irregular outline, very thin and transparent, and
very brittle when dry. During life, this shelly plate is imbedded in
the substance of the skin of the back, a thin layer of which clothes
it; so thin that it can be very readily seen and felt notwithstanding.
The mantle is much developed, forming two great irregular wing-like
lobes, which stand up on each side of the body, and at pleasure either
arch over the gill-shield, or are depressed, and widely expose it.
It is reported that these mantle-lobes are capable of being used as
swimming-fins, by their undulations; but I doubt the correctness of the
observation.
When full-grown, our Sea-hare is three inches in length, and upwards
of an inch high. Its body is of a slimy, fleshy, slug-like texture,
varying much in colour; sometimes being dark olive-green, sometimes
red-brown, sometimes deep purple, occasionally clouded with blue:
sometimes the hue is uniform; at others, it is varied by light dots, or
handsomely marked with dark rings enclosing white areas. Its figure is
extremely versatile; so that, when crawling, it scarcely exhibits the
same outline for two minutes together.
See what has happened. On dropping one of the slimy beasts into this
phial of clear sea-water, it immediately resented the incarceration
by beginning to pour out from beneath the lobes of the mantle a thin
stream of fluid of the most royal purple hue, which freely diffused
itself through the water. And see! it is still copiously exuding; and
the whole contents of the bottle are now fast becoming of so fine and
rich a tinge, as already to veil the form of the animal. Attempts
have been made to employ this secretion in the arts; but the hue is
fleeting. According to Cuvier, it assumes in drying the beautiful
deep hue of the flower known as the sweet scabious, and remains
long unaltered by exposure to the air. The purple tint is readily
transferred to spirit, when the animal is immersed in it; the tincture
retains the colour for a while, but ultimately becomes of a deep clear
port-wine tint. Linen, dyed with the fluid, soon fades to a dingy brown.
It is a curious coincidence that this mollusk possesses a more
recondite analogy with herbivorous mammalia, than a fleeting
resemblance of form. Professor Grant has shown that it has three
stomachs, like the ruminants. First, a short narrow gullet dilates
into a large membranous crop; a curved bag, which is generally filled
with pieces of coarse sea-weed. This large crop or paunch occupies the
right side of the body, and opens laterally into the middle stomach,
which is the smallest of all, and performs the part of the gizzard. Its
coats are thickened; and the interior callous lining is besat with
firm horny processes, in the form of rhomboidal plates or molar teeth,
which serve to compress the softened vegetable matter transmitted in
small portions from the first stomach. The third cavity of this complex
apparatus is placed on the left side of the body; its interior surface
is studded with sharp, horny spines, resembling canine teeth, to pierce
and subdivide the coarse food, and thus prepare it for the action of
the gastric juice and other fluids accessory to digestion, which enter
the stomach from adjacent organs.[67]
The complexity of this structure has reference to the coarseness of
the materials on which the animal subsists; the leathery fronds of the
olive sea-weeds, which slowly and with difficulty yield their nutritive
elements to the digestive functions.
This great, flabby Sea-Slug has a mythic history full of wild romance.
Our species has been often called _depilans_, because the fluid which
exudes from it was said to have the power of causing the hair to
fall from the human head which it touched; and the common species of
Southern Europe retains the appellation in the records of science. The
Mediterranean fishermen have so great a horror of it that no bribes
will induce them to handle it willingly; and they tell strange stories
of wounds being produced, limbs being mortified, and even death itself
being caused, by accidental or foolhardy contact with the potent
creature.
Bohadsch has given, on the authority of personal observation, a
minutely circumstantial account, which it seems a hyper-scepticism to
doubt. When removed from the sea, and placed in a vessel, there exuded
a large quantity of a limpid and somewhat mucilaginous fluid, exhaling
a sweetish, sickening, peculiar smell: but besides this, and distinct
from its purple secretion, the _Aplysia_ excreted also a milky liquor,
formed in an internal conglobate gland, which seems to be analogous to
the kidney of vertebrate animals. As often as he took the _Aplysia_
from the vase of sea-water and placed it on a plate with the view of
more narrowly examining its structure, the room was filled with a
nauseous odour, compelling his wife and brother to leave the room, lest
sickness and vomiting should follow. He himself could scarcely endure
it, and during the examination had repeatedly to go out and breathe a
purer air. His hands and cheeks swelled after handling the creature for
any length of time, and as often as it ejaculated its milky secretion;
but he is uncertain whether the swelling of the face proceeded from
the halitus merely, or from his having accidentally touched it with
the hand besmeared with the liquid: probably the latter was the real
cause, for when he purposely applied some of it to his chin, some hairs
fell from the part.[68]
We may add to this account, as being in a measure confirmatory of its
probability, the statement of a perfectly dependable naturalist, Mr.
Charles Darwin, that he found a species of _Aplysia_ at St. Jago,
one of the Cape Verd Isles, from which “an acrid secretion, which is
spread over its body, causes a sharp stinging sensation, similar to
that produced by the Physalia,[69] or Portuguese man-of-war.”[70] And
yet I have myself freely handled _Aplysiæ_ in health and vigour, both
here and on the coast of Jamaica, without perceiving the slightest
unpleasant sensation.