276 THE CEPHALOPODA. $ 238. 
posed others which are longitudinal, and, lastly, of a layer of circular fibres 
directly beneath the skin.“ 
Over the entire length of the internal surface of these arms, are suckers, 
arranged in a single, double, or multiple row.” But with the Loligina, 
these suckers occur in groups of variable extent only at the extrem- 
ity of the ninth and tenth arms (tentacular arms). These suckers are 
moved by muscular fasciculi which pass from the arms and are spread upon 
the former in a ray-like manner, and which form, moreover, with the Loli- 
gina, a peduncle. 
With Tremoctopus, the suckers are cylindrical and very simple, while with 
the other Octopoda, their opening is closed by a membrane perforated cen- 
trally by an orifice which can be closed by a papilla that projects from the 
base of the sucker.© These organs are applied to objects at the moment 
when the papilla is withdrawn and removed to the base of the sucker. 
With the Loligina, the lateral walls of the suckers are very thin, extens- 
ible, and have upon their borders a horny and denticulated ring; in this 
ring the fleshy base of the sucker adjusts itself in an urceolate form, and 
upon withdrawal, produces a vacuum. With Loligopsis, and Onychoteuthis, 
many of the suckers on the two tentacular arms are imperfect, but, on the 
other hand, some of the teeth of their horny border are disproportionably 
developed, or the whole is changed into a strong claw. 
The arm-like processes about the mouth of Nawtilus differ very much 
from the preceding. 
They have no trace of suctorial organs, and are 
composed of thirty-eight prismatic filaments, which are a little flattened and 
transversely curled. 
Each of these filaments is surrounded, at its base, by a contractile sheath 
into which it can be wholly withdrawn. 
The whole fasciculus is, moreover, 
enveloped in a common sheath, which, upon the back, is flattened so as to 
resemble the foot of the Gasteropoda, and like it, probably, may serve for 
creeping.” 
The portion of the skin, which extends as a kind of Natatory membrane. 
between the arms of many Cephalopoda, contains a very loose net-work of 
longitudinal and transverse muscular fibres.© 
The fins of the Loligina, have, on the contrary, large muscles composed 
of parallel, contiguous fasciculi which arise from the cartilages of these 
organs. 
1 This axis is usually of a prismatic form ; con- 
sequently if an arm 1s cut transversely the section 
presents a quadrilateral or rhomboidal spot in its 
centre ; see Sauigny, in the Descript. de Phgypte, 
Hist. Nat. Pl. I. tig. I. w.; Owen, in the Cyclop. 
I. p. 528, fig. 214, c, and Férussac, loc. cit. Octo- 
pus, Pi. IL fig. 3, and Pl. XV. fig.11,b. Asim- 
ilar section of the body of an Hectocotylus pre 
sents a like aspect. 
2 The suckers form a single row with Eledove ; 
a double one with the other Octopoda, and with 
most of the Loligina ; but the rows are muitiple 
with Sepia. 
3 Although the double row of suckers on the 
body of Hectocotylus does not diminish towards 
the anterior extremity, yet, in other respects, it so 
closely resembles the suckers of Argonauta and 
Tremoctopus, that it may wail be asked why this 
single fact was not sufficient to discover to the old~ 
er observers the real nature of this pretended par- 
asite. 
4 Férussac, loc. cit. Loligopsis, Pl. IV. and 
Onychoteuthis, Pl. VI. VIII. &c. 
5 Owen, and Valenciennes, loc. cit. 
6 The internal structure of these filaments agrees- 
pretty closely with that of the arms of other Ce- 
phalopoda. Owen, On Cephalopods with chamber- 
ed shells, loc. cit. p. 8, fig. 181, Cyclop. loc. cit. p. 
ones fig. 218, and Annals of Nat. Hist. XII. p. 
305, 
7 Owen, and Valenciennes, loc. cit. 
8 The large cutaneous lobes of the median dorsal 
arms of T'remoctopus and Argonauta, have a 
similar structure. In this last genus, they are nat 
used as oars, nor as sails, but are thrown back 
upon the shell to keep it in place (§ 285, note 4) 5 
they move in the water, moreover, like the other 
Cephalopoda, by the contractions of the mantle and 
the funnel (Rang, Magaz. d. Zool. 1837, p. 22. Pl. 
LXXXVII.). It is therefore astonishing that Jea- 
nette Power (Wiegmann’s Arch. 1845, I. p. 373) 
should have revived the old fable that these ani- 
mals raise these two large arms above the surface 
of the sea to be used as sails. 
