264 
ties. In both groups the inner surfaces of the arms, and the 
posterior inner face of tentacular organs, are provided with 
suckers. In the Argonaut, the superior pair of arms are 
produced into broad, extensible membranes, suitable for 
embracing and protecting the thin, papery shell. * 
The Acetahulay or suckers, are cup like, and usually 
round bodies, containing a soft fleshy pimple, situated in 
their central cavity; by the aid of a circle of radiating 
muscles, this pimple may be depressed, and thus a vacuum 
be produced, enabling the sucker to attach itself strongly to 
any desired object. In the Odopods the suckers are sessile, 
and in the genera Eledone and Cirroteuthis f are arranged 
upon the arms in single rows, but form two lines on each 
arm in the genera Octopus ^ Philonexis, and Argonauta. In 
the Decapoda, the suckers are placed in two alternating 
lines on each arm, except in the genus Sepia, which has four 
rows of suckers displayed on each arm. In the Decapods 
the suckers are borne on a pedicel, or stalk, and have their 
muscular portion strengthened by the presence of flat, circu- 
lar, horny rings. In the genera Onychoteuthis, Enoploteu- 
this, and some others, the arms, or tentacles, or both, are 
ai-med by rows of horny hooks and spines. 
The arms are sometimes of enormous length . Mr. John- 
son cites a Madame Graham as having seen a Cuttle Fish 
with arms 18 feet long ; and Schwediaver reports that a 
whaler harpooned a Cachalot, having in its mouth the arm 
of a Cuttle Fish nearly 23 feet long. M. HartingJ has de- 
scribed the remains of some gigantic Cephalopods preserved 
in the Museums of Utrecht and Amsterdam, wliich prove the 
* For the Anatomy of the Argonaut, see " Memoire sur I'Argouaute par." 
P. J. Van Beneden. Brux, 1838. 
f See " Cirroteuthis Miilleri eine neue Gattung der Cejphalopoden bildcnd,"' 
von Dr. Eschricht. Copenhagen, 1836. 
I " Description de quelqncs fragments de Deux Cephalopodes Gigan- 
iesques." P. Harting, Amsterdam, 1860. 
