SI 2 



Cephalopoda.- 



-MOLLUSCA.- 



-Akgonauts. 



arms are unequal, and tbe siphunole is elongate, conical, 

 and slender. The Octopi live on rocks on the coast, 

 Bwim well, and are very agile. Tliey 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, Gesuer, &c. " Professor E. Forbes 

 h;is observed that the Octopus when resting, coils its 

 dorsal arms over its back, and seems to shadow forth 

 the Argonaut's sliell." — {Woodward.) 



THE COMMON OCTOPUS (0. vuhjans) 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 tlie whole of 

 its arms, webbed at the base, at tlie 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.— FHILONEXID.E. 



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 noctimial in their habits of life. 

 I'hey are gregarious and sociable, and in some parts 

 of the world are seen during the night covering tlie 

 surface of tlie ocean in great numbers. They avoid 

 the light, possess the faculty of changing their colour, 

 and are voracious creatures, feeding upon floating 

 mollusca and medusa. 



Genus Piiilonexis.— The genus Phihnexis is the 

 type. It has the arms free, not webbed, tapering ; in 

 some species the upper pair are very long, and the 

 others short. 



Fa.\iii.y Ii(,.-ARGONAUTID^E=OCYTHOIIi^ 

 {Argonauts.) 



Tlie 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 witlr 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 tlie Argonaut shell is a mere parasite ; others 

 maintaining, on tlie 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 .leannette Power, 

 supported in most things by those of M. Sander Rang, 

 are sufficient to convince most people. Professor Owen 

 has given a very able report upon tliese c.Kperiments, 



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 Cepli<dopoda Antrprdia, 

 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 

 body appears to cause no uneasiness to the animal, as 

 it does in all other shell-bearing mollusca, where tlie 

 animal immediately rids itself of the irritation so caused 

 by covering the sand, &c., with a calcareous coat. The 

 animals, he continues, found in tliese 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 sliould 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 

 characters of the family. The animals were named 

 Ocythoe by Rafinesque, who consiilered 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 uuequal, the dorsal pair 

 being bent back on themselves, and furnished with a 

 membrane or web at the extremity. The cups are in 

 two rows, prominent, as if slightly pediceled. The 

 siphuncle is ver}' 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, ami 

 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 eivjoys 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 Arffotiatita, by those who believe in the identity 

 of shell and animal, and Ocythoe by those who do not 

 — the name oi Argonauta being restricted by them for 

 the shell alone. 



THE PAPER NAUTILUS {Arfinnauta-Argo)~{\\e 

 animal being the Ocythoe tidicrcidata of the British 

 Museum catalogue — (Plate 3, fig. 8) — is, from its being 



