312 Cephalopoda. MOLLUSCA. Akgonauts. 
arms are unequal, and the sipliuncle is elongate, conical, 
and slender. The Octopi live on rocks on the coast, 
swim well, and are very agile. They change their 
colour rapidly, and in the dark are slightly phos- 
phorescent. The females deposit transparent eggs in 
bunches on sea-weeds, or in the cavities of empty 
shells. They are solitary animals, and are the “ polypi ” 
of Homer, Aristotle, Gesner, &c. “Professor E. Forbes 
has observed that the Octopus when resting, coils its 
dorsal arms over its back, and seems to shadow forth 
the Argonaut’s shell.” — {Woodward.) 
THE COMMON OCTOPUS (0. vuUjaris) is abundant 
on our coasts, and is found in the Mediterranean, 
Atlantic, and Indian oceans, and in the Red Sea. In 
swimming, it propels itself rapidly backwards, by 
repeatedly striking in a forward direction the whole of 
its arms, webbed at the base, at the same instant. It 
walks also with equal ease, dragging its body along the 
ground at the rate of about seven feet in a minute ; 
and should it require or wish to accelerate its pace, it 
inflates its body until it resembles a distended bladder, 
then letting go all hold and casting itself forward, it 
rolls over and over with great velocity, and often effects 
an escape which would otherwise have been impossible. 
Family II.— PHILONEXIDiE. 
In this family the arms are elongate, tapering, and 
unequal ; and the cups are fleshy, pedunculated, very 
extensible, and placed in two rows, which are some- 
times far apart. The eyes are large and prominent. 
The shell is altogether wanting. The animals belong- 
ing to this family are all natives of the high seas, and 
are crepuscular or nocturnal in their habits of life. 
They are gregarious and sociable, and in some parts 
of the world are seen during the night covering the 
surface of the ocean in great numbers. They avoid 
the light, possess the faculty of changing their colour, 
and are voracious creatures, feeding upon floating 
mollusca and medusae. 
Genus Philonexis. — The genus PJnlonexis is the 
type. It has the arms free, not webbed, taj)ering ; in 
some species the upper pair are very long, and the 
others short. 
Family III.— ARG0NAUTID^=0CYTH0ID^ 
(Arffoiiauts.) 
The family of the Argonauts is one which has given 
rise to a great deal of discussion ; some authors main- 
taining that the animals, and the shell in which they 
are found, have no further connection with each other 
than the Hermit Crab has with the shell in which it 
takes up its abode — -that the Cuttle-fish in fact which 
inhabits the Argonaut shell is a mere parasite ; others 
maintaining, on the contrary, that the shell of the 
Argonaut is really secreted by the female, and that it 
serves as a nest for containing the ova. This latter 
opinion is now almost universally received by natural- 
ists ; and the experiments of Madame Jeannette Power, 
supported in most things by those of M. Sander Rang, 
are sufficient to convince most people. Professor Owen 
has given a veiy able report upon these experiments. 
the summing up of which is clearly in favour of the 
view of their intimate connection as one and the same. 
Dr. Gray, however, still considers the question unsettled ; 
and in the catalogue of the Cephalopoda Antepedia^ 
in the collection of the British Museum, he gives his 
reasons for remaining unconvinced. The animal, he 
says, is not attached to the shell by any muscle 
(unlike all other mollusca which form the shell 
they inhabit). The animal, when alive, does not fit 
the shell, so that the shell cannot be moulded on its 
body, as in other mollusca. The skin of the animal 
which inhabits the shell is of the same texture and 
appearance as in the other naked Cephalopods; 
and the presence of sand between the shell and the 
bodjf appears to cause no uneasiness to the animal, as 
it does in all other shell-bearing mollusca, where the 
animal immediately rids itself of the irritation so caused 
by covering the sand, &c., with a calcareous coat. The 
animals, he continues, found in these shells are all 
females, and the apex of the shell is filled with very 
small eggs ; while from the large size of the young 
shell, which is seen on the apex of the true Argonaut, 
we should expect the animal which formed that shell 
to have a large egg. Believing, however, that the 
shell of the Argonaut is formed by the animal which 
alone is found to inhabit it, we proceed to give the 
chaiacters of the family. The animals were named 
Ocythoe by Rafinesque, who considered them distinct 
from the shells. Their body is of an ovoid shape,- 
enlarged in front, and smooth. The head is oblique, 
and the eyes are lateral, very large, prominent, and 
covered on the upper edge with a very thin eyelid. 
The arms are tapering, very unequal, the dorsal pair 
being bent back on themselves, and furnished with a 
membrane or w-eb at the extremity. The cups are in 
two rows, prominent, as if slightly pediceled. The 
siphuncle is very large and conical. The shell is 
exterior, symmetrical, and involuted. It is one-celled, 
thin, brittle, transparent, horny, and flexible when wet. 
The nucleus is very large and hemispherical. This 
shell is inhabited only by the female, and it is con- 
sidered to be secreted by her webbed dorsal arms. 
The male is smaller than the female, has no shell, and 
the superior arms are not webbed or expanded as in 
the female, but are pointed at the extremities. Occu- 
pying the place of the third arm on the left side, there 
is in the male an organ developed within a coloured 
sac, which is in fact an irregularly metamorphosed 
arm, containing abundance of spermatozoa, and which 
is detached as soon as the seminal fluid has been 
deposited in it. It after this enjoj's an independent 
life, and is the Hectocotyle of the Argonaut. These 
animals live on the high seas in the warmer regions, 
and have been taken from the stomach of 'a dolphin 
six hundred leagues from any land. Their food con- 
sists of floating mollusca. There is only one genus, 
called A rgonauta, by those who believe in the identity 
of shell and animal, and Ocythoe by those who do not 
— the name of Argonauta being restricted by them for 
the shell alone. 
THE PAPER NAUTILUS {Argonauta- Argo) — the 
animal being the Ocythoe tuberculata of the British 
Museum catalogue — (Plate 3, fig. 8) — is, from its being 
