Chapter XV: Molluscs

The Molluscs in general.--The Cephalopods.--Dibranchiates and
Tetrabranchiates--Arms and Tentacles.--Suckers.--Hooked Acetabula
of the Onychoteuthis.--Mandibles.--Ink Bag.--Numbers of the
Cephalopods.--Their Habits.--Their Enemies.--Their Use to Man.
--Their Eggs.--Enormous size of several species.--The fabulous
Kraken.--The Argonaut.--The Nautili.--The Cephalopods of the
Primitive Ocean.--The Gasteropods.--Their Subdivisions.--Gills of
the Nudibranchiates.--The Pleurobranchus plumula.--The Sea-Hare.
--The Chitons.--The Patellæ.--The Haliotis or Sea-Ear.--The
Carinariæ.--The Pectinibranchiates.--Variety and Beauty of their
Shells.--Their Mode of Locomotion.--Foot of the Tornatella and
Cyelostoma.--The Ianthinæ.--Sedentary Gasteropods.--The Magilus.
--Proboscis of the Whelk.--Tongue of the Limpet.--Stomach of the
Bulla, the Scyllæa, and the Sea-Hare.--Organs of Sense in the
Gasteropods.--Their Caution.--Their Enemies.--Their Defences.
--Their Use to Man.--Shell-Cameos.--The Pteropods.--Their
Organisation and Mode of Life.--The Butterflies of the Ocean.
--The Lamellibranchiate Acephala.--Their Organisation.--Siphons.
--The Pholades.--Foot of the Lamellibranchiates.--The
Razor-Shells.--The Byssus of the Pinnæ.--Defences of the
Bivalves.--Their Enemies.--The common Mussel.--Mussel Gardens.
--The Oyster.--Oyster Parks.--Oyster Rearing in the Lago di
Fusaro.--Formation of new Oyster Banks.--Pearl-fishing in Ceylon.
--How are Pearls formed?--The Tridacna gigas.--The Teredo navalis.
--The Brachiopods.--The Terebratulæ.--The Polyzoa.--The Sea-Mats.
--The Escharæ.--The Lepraliæ.--Bird's Head Processes.--The
Tunicata.--The Sea-Squirts.--The Chelyosoma.--The Botrylli.--The
Pyrosomes.--The Salpæ.--Interesting Points in the Organisation
of the Tunicata 270