MOLLUSCA. 93 
is derived. The body is obtuse posteriorly, with fins (fin-like expansions), 
and the interior dorsal shell is wanting. As the name implies, it has eight 
arms. The species figured attains a length of two feet and a half, including 
the arms, which constitute considerably the longest portion. It creeps upon 
the ground with the mouth downwards, drawing itself along by means of 
the circle of arms; or leaving the bottom, it swims backwards by flapping 
the fleshy disk from which the arms arise. It is provided with an ink bag. 
The eyes can be covered with the surrounding skin, in the manner of an 
eyelid. There are two complicated branchiz somewhat like a fern leaf, 
through which the blood is forced, by a heart at the base of each; a third 
heart, near the bottom of the cavity, receives the oxygenated blood, and dis- 
tributes it through the body. It is eaten on the shores of the Mediterranean. 
Argonauta (A. argo, Linn., pl. 76, jig. 17), six or seven inches long, has 
a closely rolled involuted shell without partitions, laterally compressed, 
tuberculate, very thin, white, translucent, with the last turn including the 
rest. This is the Nautilus of the ancient authors, who were acquainted 
with A. argo, the Mediterranean species, about the sailing of which so many 
fables have been related, as in the following lines from the “ Pelican Island.” 
“ Light as a flake of foam upon the wind, 
Keel upwards from the deep emerged a shell, 
Shaped like the moon ere half her horn is filled ; 
Fraught with young life, it righted as it rose, 
And moved at will along the yielding water. 
The native pilot of this little bark, 
Put out a tier of oars on either side, 
Spread to the wafting breeze a twofold sail, 
And mounted up and glided down the billow 
In happy freedom, pleased to feel the air, 
And wander in the luxury of light.” 
For a long time naturalists considered the maker of the shell of Argonauta 
to be unknown, believing the inhabitant found in it to be a parasite, like 
the crabs which take possession of the empty shells of the spirivalve 
mollusca; and they were led to this belief, by the fact that there is no 
muscular attachment between the animal and the shell, presenting a 
peculiarity which is unique among the mollusca. The animal has eight 
arms, two of which have wide expansions at the extremity, which are 
applied one to each side of the shell, which is in fact secreted by their 
internal surface; and should it be intentionally broken, the damage is 
repaired by the same organs in ten or twelve days, a proof that the shell 
belongs to no other animal. It creeps upon the bottom with the shell 
above, or shoots through the water backwards by means of the funnel, with 
the narrow part of the shell in advance, and the arms extended like a 
rudder. When it retires within the shell, the expansions of the clasping 
arms are partly withdrawn, leaving a little of the anterior portion of the 
shell uncovered; consequently, they are never extended as sails, as many 
fabulous accounts would lead us to believe. See the Mag. Nat. Hist., 1839, 
pp. 421 and 521; 1840, pp. 8 and 57. 
297 
