A CUTTLE-BONE. 47 



tion, as does the pearly nautilus of to-day, or as did 

 the old extinct and fossil allies of the last-named 

 animal. They are wary and agile in all their move- 

 ments, and have apparently got rid of their shells 

 entirely ; just as the slug of the garden has re- 

 linquished his shell (seen in his young state), while 

 his neighbour the snail has retained that possession 

 of molluscan life. 



Yet closer examination reveals that the sepia and 

 octopus and other modern cuttlefishes have not wholly 

 surrendered their shell-making instinct ; for, lying on 

 their backs, imbedded in their " mantles," we find 

 shells of rudimentary description. This shell in the 

 sepia is the " cuttle-bone " of the * A 



bird-shop and drug-store. 



It is a lingering remnant of 

 shells which, once upon a time, 

 were very well developed in the 

 ancestors of the sepia and its 

 friends. It has dwindled away 

 till it has become a mere plate of Figt is ._s p iruiaand 

 lime, bearing faint and feeble traces its shell. 



of a once complex structure. In the squids or loligos, 

 which are used so largely for bait by the Newfound- 

 land fishermen, the shell has become degraded until 

 it forms a mere horny " pen." So that what my friend 

 purloined from the canary's cage is really a curious 

 example of a shell that has gone to the wall in the 

 struggle for existence, simply because it was not needed 

 in the life and wants of the modern cuttlefishes. 



This much is certain from ordinary natural history 

 science alone. If, however, we were inclined to doubt 

 the correctness of the inferences we have drawn, we 

 should be able to find additional proofs in the shape 



