An important function of the gastropod shell is to protect the body against attack by predators. If the shell of a whelk is broken away and the soft animal is then offered to a hungry cod, it is eaten readily. Many successful gastropods, however, lack an external shell as adults (although it is certain that all have evolved from shelled ancestors) and might be expected to be eaten by fish as readily as is the naked body of a broken whelk. The purpose of this paper is to describe part of an investigation into whether this is in fact true.