Juergen Freund / Marine polyclad flatworm (Polycladida)

Pascal Kobeh / Glorious flatworm (Pseudobiceros gloriosus) New Caledonia, Pacific Ocean.

David Hall / Polyclad flatworm (Pseudobiceros uniarborensis). Komodo, Indonesia.

Georgette Douwma / Glorious flatworm (Pseudobiceros gloriosus). West Papua, Indonesia. Indo-West Pacific.

Georgette Douwma / Flatworm (Pseudoceros laingensis) West Papua, Indonesia. West Indo-Pacific.

Georgette Douwma / Racing stripe flatworm (Pseudoceros bifurcus) Puerto Galera, Philippines.

Georgette Douwma / Flatworm, probably Pseudobiceros sp, West Papua, Indonesia.

Sue Daly / Candy striped flatworm (Prostheceraeus vittatus) laying eggs, Isle of Man, July.

Constantinos Petrinos / Marine flatworm (Phrikoceros sp.) Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Marine flatworm (Pseudobiceros flowersi) with ruffled marginal tentacles - pseudotentacles. Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Marine flatworm (Pseudobiceros flowersi) with ruffled marginal tentacles - pseudotentacles. Lembeh Strait, North Sulawesi, Indonesia.e shown that fish will spit them out after the briefest of nips. We...

Georgette Douwma / Polyclad flatworm (Pseudobiceros fulgor). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Flatworm (Maiazoon orsaki) gliding over sponge Mabul, Indonesia.

Georgette Douwma / Symmetrical flatworm (Pseudoceros dimidiatus) Mabul, Malaysia.

Alex Mustard / Undescribed species of flatworm (Cycloporus sp.) crawls over a sea squirt. Mioskon Island, Raja Ampat, West Papua, Indonesia. Dampier Strait. Tropical West Pacific Ocean

Sue Daly / Candy striped flatworm (Prostheceraeus vittatus) Guillaumesse, Sark, British Channel Islands.

Juergen Freund / Polyclad flatworm (Maiazoon orsaki) Papua New Guinea

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Close-up of marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus) close-up, Great Barrier Reef, Australia.

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus), dorsal view, Great Barrier Reef, Australia.

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus), dorsal view, Great Barrier Reef, Australia.

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus), dorsal view, Great Barrier Reef, Australia.

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus) close-up, Great Barrier Reef, Australia.

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Marine polyclad flatworm (Polycladida)

Juergen Freund / Fuchsia flatworm (Pseudoceros ferrugineus), dorsal view, Great Barrier Reef, Australia.

Alex Mustard / Flatworm (Cycloporus sp.) resting inside a Sea squirt (Didemnum molle) on a coral reef, Raja Ampat, West Papua, Pacific Ocean.

Sergio Hanquet / Flatworm (Thysanozoon sp.), moving over stones through undulating ripples of body, Tenerife, Canary Islands, Atlantic ocean.

Georgette Douwma / Composite image of marine invertebrates on black background. Top row from left: Tube anemone (Ceriantharia), Yellow sea cucumber (Colochirus robustus), Nudibranch (Nembrotha lineolata), Squat shri...

Franco Banfi / Flat worm (Prostheceraeus sp.) on coral, rare albino species which inhabits poorly lit environments, Vis Island, Croatia, Adriatic Sea, Mediterranean.

David Fleetham / A pair of marine flatworms (Thysanzoon nigropapilosus) on coral, Yap, Micronesia.

David Fleetham / A yet unnamed Flatworm (Paraplanocera sp.) which has been known to science for sometime but is yet to be named. It has been seen in the Marshall Islands, the Red Sea, Papua New Guinea the Galapagos Is...

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

David Fleetham / Gold rim flatworm (Pseudoceros paralaticlavus) at night, Hawaii.

Georgette Douwma / Flatworm (Pseudoceros sp) in coral reef. Derawan Islands, East Kalimantan, Indonesia.