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Exhalent water current leaves animal via anal siphon at rear of space enclosed by parapodium, taking faeces with it.
When irritated, glands under mantle edge readily emit mixture of mucus and purple dye which persists for long enough to allow Aplysia to escape under its screen.
Emission of purple most vigorous near posterior of parapodium where exhalent/anal siphon located; like smoke from a funnel in this image.

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