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MANUAL OF ZOOLOGY 



there is no shell in the male, but the female has an external 

 shell (Fig. 176) of a remarkable character. It is a 

 delicate spiral structure, the internal cavity of which is not 

 divided into chambers ; and it is not secreted by the mantle 



FIG. 175. LoligO VUlgaris. A, entire animal, dorsal view ; B, horny internal shell 

 or pen. (From Keferstein.) 



like the shells of other Mollusca, but by the surfaces of a 

 pair of the arms ending in expanded disc-like extremities, 

 which become applied to its outer surface ; its chief function 

 is to carry the eggs. 



