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Larger context for LACK in Corpus USbrown_UKbncw/UK_bncw.txt

  The proboscis can be extended to a length roughly equal to that of the whelk's own shell (Fig. 2).   Should it be lost or damaged, it can be regenerated quickly.   In Nucella the hole bored through the victim's shell is large enough to take the proboscis, and the whelk does not need to alter position on its prey once the hole is completed.   This is not the case In at least one species of the related genus Thais which has shifted position after injecting the narcotic and feeds at the gaping edge of the victim's shell (Carriker, 1981).   It is obviously impractical to have bulky salivary glands in the slender retractile proboscis and they lie at its inner end, anterior of the cerebral commissure.   lack >   In most prosobranchs, the saliva lack s any digestive function, being predominantly mucous and functioning as a lubricant for the food collecting and swallowing activities of the animal.     The carnivorous whelks, however, secrete several proteolytic enzymes (Fretter and Graham, 1962).   Prey Selection Throughout its geographical range, Nucella lapillus has a choice of prey species.   It follows that the snails show a pattern of prey selection.   Such patterns might be based on prey size, prey distribution, prey abundance or prey value.