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INVERTEBRATA. TYPE MOLLUSCA. 

 CHAPTER I. 



THK CEPHALOPODA. 



Cephalopoda Derivation of the Term Unexpected Relationships Shells Utility of Aquaria General Characters of the 

 "Naked" Cephalopods Clas- id cation : the Dibranchiata and Tetrabranchiata Their Mode of Locomotion The Mouth 

 and Eyes Means of Escape and Defence Representative Dibranchiates in the Ancient "World DIBRANCHIATA, 

 OCTOPODA-AKGONAUTID.E The Argonaut, or Paper Nautilus Its Fabled Position Its Praises as Sung by the 

 Poets How the Nautilus really Swims The True Uses of the Arms Curious Fact regarding the Shell The Male 

 as Compared with the Female The " Hectocotylus "Species of Argonaut OCTOFODID.E The Common Octopus 

 Appearance Formidable Seizing Organs Owen's Description of the Tentacles Mechanism of the Suckers The 

 Octopods of Leghorn The Octopus of the Greeks Mr. Darwin's Account of the Octopus A Diver Attacked The 

 Adventures of an Octopus in an Aquarium Spawning Season Eggs of the Octopus- Henry Lee's Observations as 

 to the Hatching of the Eggs The Baby Octopus New Growth of Amputated Limbs Food for Predatory Fishes 

 Contests with the Conger Eel The "Devil-fish" and Nursehottnd Various Species of Octopus De Montfort's 

 Gigantic Octopus Cuttles and Octopus as Diet Octopus Fishery DECAPODA TEUTHID^E Distinctive Features 

 The Tentacles Suckers Shell Remarkable Skin Characters Play of Colours THE COMMON SQUID "Pen-and- 

 ink Fish" Their Spawn The "Little Squids "The Nerve-masses of the Dibranchiata A Tom Thumb Cephalopod 

 Loliffopsis CheiroteutkisHistioteutkis The Clawed Calamary Construction of the Suckers of the Calamary 

 The Armed Calamary The Sagittated Calamary " Sea-arrows " Squid-bait The Cod-fishery Squid-jigging 

 The Giant Cephalopods Instances of their being Met with, and of their Capture Sir Francis Chantrey and Fossil 

 Ink BELEMNITID^E No Living Representative What the Fossil really is Species SEPIAD.E The Common Cuttle- 

 fish Beautiful Coloration The Bone or Shell The Cranial Cartilage in the Cuttle The Heart Movements in 

 the Water Not Long-lived in Confinement, and why The Cuttle's Eye The " Ink-bag " Discharge of the Ink 

 Use of the Ink The Eggs of the Cuttle Young Cuttles Uses of the "Bone" Various Species of Sepia The 

 Cuttle as an Article of Diet SPIRULITXE Genus Spirula Remarkable Characters Rarity Difficulty of Studying it 

 Peculiar Shell Characters ORDER TETRABRANCHIATA NAUTILIAD.E External-shelled Cephalopods Nautilus 

 and Spirula the only Siphonated Shells Living Construction of the Shell Rumphius's Account of the Pearly 

 Nautilus Mr. Moseley's Observations How the Animal Moves Abundance Various Parts of the Nautilus The 

 Air-chambers The Uses of the Siphuncle Formation of the Septa Fossil Members of the Tetrabranchiata. 



CLASS I. CEPHALOPODA. 



ONE of the foremost groups in the Molluscan division or type of the Invertebrata is that of the class- 

 Cephalopoda*, so called by Cuvier, because the animals included in it have their feet or tentacles 

 attached to the head, around the mouth, a simple and convenient arrangement for taking in food, 

 which we shall presently find repeated in some other groups, such as the Stone Lilies and Sea 

 Anemones, &c., nutrition being the highest ambition of the lives of at least a large majority of 

 these animals. 



The Octopus, or " devil-fish," the Cuttle-fish, and the Pearly Nautilus are excellent examples of 

 these head-footed Mollusca, which (like the Sharks among existing fishes) represent at once a very 

 ancient and singular group, but are nevertheless true Mollusca. The Garden Snail does not appeal-, 

 on a cursory inspection, to have much in common with the " Sea Squid," or the " Cuttle-fish," 

 but the Garden Snail is first cousin to the Slug, which has no visible shell, and the shell-less, 

 Octopus is next-of-kin to the Pearly Nautilus, which carries its shell upon its back. 



Thanks to our public museums, we have long been familiar with those beautiful objects, Shells ; 

 and every schoolboy knows the look of the commoner forms of living Mollusca, such as Snails, 

 Whelks, Mussels, Oysters, and Cockles, but it is only within the last few years that the introduction of 

 Marine Aquaria in many of our large cities has made us really acquainted with sea-shells and their 

 inhabitants in a living state. To these establishments we are more especially indebted for a 

 knowledge of such forms as the Cuttle-fish and Octopus and their relatives, seldom seen upon our 

 sea-shores, of which we have first to speak. 



By far the larger part of the existing members of this great division of the Mollusca, or soft-bodied 

 animals, are unrepresented in museums or cabinets of shells, ssither because, like the Octopus, they 

 have no shell, or, like the Squids, Calamaries, and Cuttles, they have only an internal one, which in. 

 often very delicate and not easily preserved. But this is not the case with all the Cephalopoda ; 

 for the Pearly Nautilus has as solid and compact a shell as any to be found among the whole- 

 Molluscan group, and so had the old fossil forms of Nautilus and Ammonite, of Goniatite 

 and Orthoceras, whose chambered shells are to be met with preserved as fossils in rocks of venr 

 different ages and countries all over the globe. 



* From kephale, Gr , a head, and pous, Gr., a foot. 



