528 Natural History of Molluscous Animals : — 
bed arms at the same’ instant.” * Mr. Cranch likewise informs 
us, that the parasitical and finless Ocythoé swim freely when 
out of their shell, having, as he adds, all the actions of the 
common Octdpus of our seas. ‘These quotations, we pre- 
sume, will be deemed conclusive; and, from the first, we learn 
by what organs they swim. It is by means of the tentacula 
just mentioned ; long tapered organs, which encircle the head 
as with a crown, are capable of being inflected in every direc- 
tion, and, in this tribe, are edged with a web-like membrane, 
serving to unite them all together towards their origins. 
Desmarest has observed the Octopodize to have another mode 
of progression, and one very unusual amongst animals; viz. 
by rolling over upon themselves with great velocity, and 
without fixing themselves by their tentacula. + 
Some t¢ of this tribe, as I formerly hinted, take possession 
of the shelf of the paper nautilus (Argonatita A’rgo), and make 
it their boat; a purpose for which it is admirably fitted by its 
lightness and navicular 
form. It is said that 
the Sépia’ lays over 
each side of the shelf 
three of its tentacula, 
which it uses for oars, 
and raises up other two 
dilated at their ends 
by a thin oval mem- 
brane, which fancy may 
compare to a sail, and 
which serve the pur- 
pose of one. Having, 
by a process yet unexplained, risen to the surface, this pirate 
sailor thus plies his vessel with oar and sail ; but ever timorous 
as a guilty thing, he shrinks within on the least alarm, and 
sinks again into his port, the deep. (jig. 129.) 
“ Light as a flake of foam upon the wind, 
Keel upward from the deep emerged a shell, 
Shaped like the moon ere half her horn is fill’d; 
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, 
* Edin. Phil. Journ., xvi. 313. 
+ Blainville, Man. de Malacologie, p. 149. 
{ Bose says that more than one species occupy the shell of the Argo- 
nauta A’rgo, Hist, Nat. des Vers., 1. p.90. 
