350 Aplysiiu^. MOLLUSCA, Umbkelliu,*;. 
side lobes of the foot are dilated, and free for swimming 
(see Plate 4, fig. 1 — Aplysia punctata) ; and the shell 
is subcartilaginous and covered b^' the mantle. It 
is oblong, convex, fle.xiblo, and translucent, with the 
apex acute and slightly incurved. The species of 
Sea-hares, or Aplysise, are rather numerous, upwards 
of forty having been described; they are found iidiabit- 
ing the seas of the West Indies, the Mauritius, China, 
the Mediterranean, Norway, and Great Britain. They 
are chiefly vegetable feeders, living principally on sea- 
weed. They are said to devour animal substances also ; 
but Cuvier, Pessonel, and others have sufficiently proved 
that marine plants are their ordinary food. Dr. John- 
ston tells us that he kept a specimen of the Aplysia 
mustelina for nearly three months in a state of confine- 
ment, during wliich it was fed on sea-weed alone, and 
that it ate these greedily, showing a certain degree of 
preference for the dulse {Fitcus palmatus). The 
Aplysia is of quick growth, the Mediterranean species 
being said to attain its full size of about four inches in 
one or two months. When irritated these animals pom- 
out an abundance of a fine purple-coloured fluid, so 
much so tliat a single individual can colour the water 
for some yards around it. “ This fluid is secreted in a 
gland of a triangular figure, situated under the base of the 
fleshy coverlid of the branchiae, and oozes out from all 
the free surface of this coverlid.” — {Johnston.) Cuvier 
says that, in drying, the secretion assumes the beautiful 
deep hue of the sweet Scabious (Scabiosa atro-purpu- 
reu), and remains unaltered by long exposure to the 
air. The smell is faint; there is nothing peculiar to the 
taste, nor has it any irritating quality, for it may be 
applied a long time to the skin with perfect impunity. 
Besides this innocuous purple fluid, the Aplysiae occa- 
sionally discharge, though only in small quantities, a 
whitish liquid of an acrid nature, which is secreted by 
a gland composed of little round hyaline grains, and 
emitted through a eircular aperture opening externally 
a little behind the aperture of the oviduct. On this 
account, and from their grotesque forms, in olden times 
they were viewed with fear and superstitious dread ; 
they were considered, by the Romans especially, as 
possessing a deadly poison. “ It was held, or was sup- 
posed to hold,” says Dr. Johnston, “such a noxious 
sympathy with man, that the ‘only aspect thereof’ was 
poisonous to some ; to women great with child the sight 
produced untimely labour, and hence it was employed 
to discover concealed pregnancy ; the touch of it was 
fatal, some say, to the man who handled, others to the 
mollusc, which latter doubtless would be the more pro- 
bable result ; while others affirmed only that the hair 
fell from the parts with which it came in contact; and 
all agreed that the odious foetor which issued from the 
body occasioned sickness and overturnings of the sto- 
mach. ■ That such a creature should, afford a potent 
poison was a reasonable inference ; and it certainly 
formed one ingredient of some of the poisonous draughts 
so much resorted to in the corrupt days of Rome. 
Locusta used it to destroy such as were inimical to Nero; 
it entered into the fatal potion which she prepared for 
the tyrant himself, and which he had not resolution to 
swallow ; and Domitian was accused of having given it 
to his brother Titus. The operation of the poison was 
not immediate ; but tbe victim lived as many days as 
the hare had lived subsequent to its removal from the 
sea. What proportion of truth there is in this account 
it is not easy to decide. I am not prepared to reject the 
whole, as some modern authors have done, who believe 
that the singular conformation of the Aplysia, and the 
power it possesses of discharging at pleasure large 
quantities of a fluid of the richest purple colour, have 
given rise to the whole tale.” Our British species ap- 
pear to be perfectly inoffensive and quite harmless; but 
there may be other species in warmer climates, which, 
at particular times, may possess a fluid of deleterious 
quality. Bohadtch, an author of some repute, mentions 
that one speeies which abounds in the Bay of Naples, 
(the Aplysia leporina), when removed from the sea 
and placed in a vessel, exuded a large quantity of fluid 
which exhaled a sweetish, sickening, peculiar smell. 
When placed on a plate for the purpose of more nar- 
rowly examining its structure, the room, he says, was 
filled with a most fetid, nauseous odour, which he could 
scarce endure without going out repeatedly to breathe 
a purer air. His hands and cheeks swelled after hand- 
ling the creature for any length of time, and when he 
applied some of the liquid to the chin, the hairs fell from 
the part touched. In a large species which occurs at 
St. lago, in the Cape de Verd Islands, Mr. Darwin 
informs us that, besides emitting a purple fluid whieh 
stained the water for the space of a foot around, it dis- 
charged an acrid secretion from all over its body, which 
caused a sharp, stinging sensation similar to that pro- 
duced by the Physalia or Portuguese man-of-war. 
Aplysia depilans is the mo.st common of the species in 
our seas, and obtains its specific name from its supposed 
depilatory powers. 
Family— UMBRELLIDAE {Umbrella Shells.) 
The Umbrellas have a regularly calcareous, exter- 
nal shell, but very disproportionate to the size of the 
animal. The foot is very large, thick, tubercular on 
its sides ; it is flat beneath and deeply notched in front. 
In this fissure is placed the mouth, which is furnished 
with a retractile proboscis. The shell is limpet-like, 
orbicular, flattened, with a slightly raised, conical, sub- 
central apex. Externally it is marked by concentric 
lines of growth, and internally it has a central coloured 
and striated disk.— See Plate 5, tigs. I, 2 {Umbrella 
umbellata and animal). 
Order II.— NUDIBEANCHIATA (= Gymnobranchiata.) 
The Nudibranch or Naked-gilled Molluscs, or “ Sea carry their gills, which are of various forms, on some 
Slugs,” as they are frequently called, are all natives of part of the back, exposed to the direct influence of the 
the sea. They have no shell in their adult state, and water in which they live. They possess an elongate 
