Mollusca. 77 



pre} T with their suckers. Food consists chiefly of crabs which, after being 

 caught and carried to the mouth by means of the arms, are quickly pa- 

 ralyzed by a poisonous fluid secreted by the salivary glands. Then the 

 juices are sucked out of the body, the solid parts not being swallowed. 

 The Octopus are strong and daring robbers, lying in wait for their pre}>- 

 in the crevices of the rocks. In the Aquarium they pile up large stones 

 into a heap behind which they conceal themselves, ready to pounce out 

 on the unwary fishes; their power of changing their colour and of pro- 

 ducing all sorts of warts and wrinkles on their otherwise smooth skin 

 enables them to counterfeit so closely their surroundings, that they can 

 only be distinguished with difficulty. They are caught all round the coast 

 of the Mediterranean , allured by baits , upon which they pounce and 

 with which they are hauled up. They are found in all Neapolitan fish 

 markets, as they are ofthen eaten, and the arms of young specimens are 

 especially esteemed. 



A very near ally of Octopus is Eledone moschata. the Musk-octopus, 

 much smaller and with only one row of suckers on each arm. They are 

 very shy and try to hide themselves from view. When taken out of the 

 water they give out a strong odour of musk. As they are frequent in 

 occurrence they are often brought to market, but are generally only eaten 

 ay the common people. 



One of the interesting and most important of the Cephalopods is the 

 Sepia or Cuttlefish (Sepia officinalis , Fig. 78). Their body is oval, 

 somewhat flattened, and with a membranous fin running down both sides. 

 Beneath the dorsal skin is the cuttle-bone , found often on the En- 

 glish coast and given to captive canaries to sharpen their beaks. Tho 

 eight arms are much shorter than those of the Octopus and are generally 

 carried closely applied together ; between them is hidden another much 

 longer pair of arms which can be shot out to catch crabs .or fish. 



The most noticeable characters in Sepia are the excretion of an inky 

 fluid and the change of colouring in the skin. Both of these they have 

 in common with the other Cephalopods , but they make more frequent 

 use of them. The sepia used by artists is the product of a gland, the 

 so-called ink-sack . the contents of which can be squirted out through 

 the funnel; a small quantity is enough to suddenly envelop the animal 

 in a black cloud, which hides it from its pursuer. The ink is extracted, 

 dried and brought to marcket ; even that of fossil species can still be 

 used. The wonderful play of colours on the living animal is due to 

 large cells (chromatophores) which are situated in the skin and are filled 

 with finely divided dark colouring matter: as these cells contract (become 

 globular) and expand (become flat), a continuous change of colours takes 

 place; stripes, spots and markings make their appearance and disappear 

 according as the animal is at rest or is irritated. The Cuttlefish have 

 complete control over this change of colours ; this is seen from the pro- 

 tective colouring , which they assume when they lie on the sand or on 

 dark rocky ground : in either case they can hardly be distinguished. 

 The males court the females with great ardour, and in their excited state 

 produce most brilliant colours over their body. The female lays large, 



