Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Steve Downer / Yellow slug larva (Limax flavus) emerging from an egg case, controlled conditions.

Steve Downer / Yellow slug larva (Limax flavus) emerging from an egg case, controlled conditions.

Piotr Naskrecki / Ground Frog (Platymantis boulengeri) female protecting her clutch of eggs, Papua New Guinea

Ernie Janes / Four Domestic ducklings and one duck egg

Birgitte Wilms / Nudibranch laying eggs, Indonesia

Chris Newbert / Yellow-striped Cardinalfish (Apogon cyanosoma) male with eggs in mouth, 40 feet deep, Solomon Islands

Nigel Cattlin / Large white butterfly (Pieris brassicae) eggs on underside of Nasturtium (Tropaeolum majus) leaf. Berkshire, England, UK. August.

Nigel Cattlin / Large white butterfly (Pieris brassicae) eggs on underside of Nasturtium (Tropaeolum majus) leaf. Berkshire, England, UK. August.

Nigel Cattlin / Large white butterfly (Pieris brassicae) eggs on underside of Nasturtium (Tropaeolum majus) leaf. Berkshire, England, UK. August.

Tony Wu / Korean sandlance (Hypoptychus dybowskii) egg clusters on Sargassum (Sargassum horneri). Fish produce sticky secretion in kidneys that adheres eggs to Sargassum. Hokkaido, Japan. May.

David Perpinan / Radiography of a captive female red-eared slider (Trachemys scripta) showing eggs within the uterus. Captive animal. Small repro only

Andy Sands / Small blue butterfly (Cupido minimus) female laying eggs among flowers of Kidney Vetch (Anthyllis vulneraria), Hertfordshire, England, UK, May

Gary Bell/ Oceanwide / Yellow-striped Cardinalfish (Apogon cyanosoma) male aerating eggs held inside mouth, Great Barrier Reef, Australia

Robert Thompson / Dog vomit slime mold (Fuligo septica) and slug on moss. Annagarriff Wood National Nature Reserve, Peatlands Park, County Armagh, Northern Ireland. August.

Alex Mustard / Yellow wentletrap snail (Epitonium sp.) feeding on Cup coral (Tubastraea sp.). Snail laying clutch of eggs. Nusa Kode, Rinca Island, Komodo National Park, Indonesia. South East Asia. Horseshoe Bay, Sa...

Adrian Davies / Dog vomit slime mould (Fuligo septica). Sussex, England, UK. October.

Alex Mustard / Weedy seadragon (Phyllopteryx taeniolatus) male carries eggs through a kelp forest (Macrocystis pyrifera) in Tasmania, Australia. Tasmania is the only part of Australia with giant kelp forests. The ke...

Robert Thompson / Slime mould (Fuligo septica) Annagarrif Wood NNR, Peatlands, County Armagh, Northern Ireland, September.

Sue Daly / Egg wrack (Ascophyllum nodosum), Herm, British Channel Islands, June.

Steve Downer / Yellow slug (Limax flavus) back lit embryos moving around in egg cases.

Steve Downer / Yellow slug (Limax flavus) back lit embryos moving around in egg cases.

Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Steve Downer / Yellow slug (Limax flavus) back lit embryo moving around in egg case.

Wild Wonders of Europe / Widstrand / Yellow-legged gull (Larus michahellis) eggs in nest, Velebit Mountains Nature Park, Croatia, April 2014.

Nick Upton / Pair of Common blue damselflies (Enallagma cyathigerum) attempting laying eggs under a Yellow water lily (Nuphar lutea) leaf, Cornwall, England, UK, June.

Nick Upton / Pair of Common blue damselflies (Enallagma cyathigerum) attempting laying eggs under a Yellow water lily (Nuphar lutea) leaf, Cornwall, England, UK, June.

Nick Upton / Pair of Common blue damselflies (Enallagma cyathigerum) attempting laying eggs under a Yellow water lily (Nuphar lutea) leaf, Cornwall, England, UK, June.

Nick Upton / Female Common blue damselfly (Enallagma cyathigerum) laying eggs under a Yellow water lily (Nuphar lutea) leaf as the male clasps her behind the head, before they fly in tandem and reposition a couple...

Nick Upton / Female Common blue damselfly (Enallagma cyathigerum) laying eggs under a Yellow water lily (Nuphar lutea) leaf as the male clasps her behind the head, Cornwall, England, UK, June.

Ingo Arndt / Egg of Emperor swallowtail butterfly (Papilio ophidicephalus) on leaf, Africa

Tony Wu / Hairchin goby (Sagamia geneionema) eggs. Though still early in development, individual transparent fish embryos are visible attached to the yellow-orange yolk sacs. Miho, Shizuoka Prefecture, Japan, P...

Andy Sands / Braconid (Agathidinae sp.) ovipositing into Fleabane seedhead, Oxfordshire, England, UK, September

Andy Sands / Braconid (Agathidinae sp.) Ovipositing into fleabane seedhead, Oxfordshire, England, UK, September

Gerrit Vyn / Yellow-headed blackbird (Xanthocephalus xanthocephalus) nest and eggs. Sublette County, Wyoming. June.

Rolf Nussbaumer / Sleepy Orange (Eurema nicippe), newly hatched caterpillar eating egg case, Texas, USA. June

Alex Mustard / Saddleback anemonefish (Amphiprion polymnus) adult bares its teeth while guarding its newly laid eggs, Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Pacific Ocean.

Tony Wu / Five-lined cardinalfish (Cheilodipterus quinquelineatus) with mouthful of yellow eggs, Ambon, Indonesia

Nick Hawkins / Yellow-spotted salamander eggs (Ambystoma maculatum) showing symbiosis with green algae, New Brunswick, Canada, May 2015.

Franco Banfi / Lumpsucker (Cyclopterus lumpus) yellow egg mass, Little Strytan dive site, Eyjafjordur nearby to Akureyri, northern Iceland, North Atlantic Ocean.

Franco Banfi / Lumpsucker (Cyclopterus lumpus) male animal guarding his yellow egg mass, Little Strytan dive site, Eyjafjordur nearby to Akureyri, northern Iceland, North Atlantic Ocean.

Andy Sands / Slime mold (Fuligo septica) on dead silver birch log, Buckinghamshire, England, UK, November. Focus stacked image.

Andy Sands / Slime mold (Fuligo septica) plasmodia slime mold on dead wood, Buckinghamshire, England, UK, November . Focus stacked image

Andy Sands / Large white butterfly (Pieris brassicae) close up side view of newly laid eggs showing yellow coloured yolk inside, UK, captive . Focus stacked image - sequence 1 of 2

Gerrit Vyn / Eastern Yellow Wagtail (Motacilla tschutschensis) nest and eggs, Yukon Delta National Wildlife Refuge, Alaska, USA June.

ZSSD / Golden Mantella (Mantella aurantiaca) female with eggs, San Diego Zoo, California

Alex Mustard / Saddleback anemonefish (Amphiprion polymnus) female barks as she guards her clutch of eggs, laid beneath her host anemone. Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pa...

Alex Hyde / Egg of Common swallowtail butterfly (Papilio machaon) on Umbellifer flower, Julian Alps, Slovenia. July.

Alex Hyde / Various seaweeds stranded on a beach including Sea belt / Devil's apron (Laminaria saccharina) and Knotted / Egg wrack (Ascophyllum nodosum) Isle of Mull, Scotland, UK. June.

Georgette Douwma / Three-spot damsel (Dascyllus trimaculatus) guarding eggs. Egypt, Red Sea.

Alex Hyde / Eggs of Green Dock Beetle (Gastrophysa viridula) on underside of Broad-leaved Dock leaf (Rumex obtusifolius). Peak District National Park, Derbyshire, UK. May.

Pete Oxford / Giant Owl Butterfly Caterpillar (Caligo memnon) with eggs laid on neck area by parasitic wasp. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Kim Taylor / Yellow slime mould (Fuligo septica) growing on a rotting pine stump, Surrey, England, April.

Kim Taylor / Yellow slime mould (Fuligo septica) growing on a rotting pine stump, Surrey, England, April.

Kim Taylor / Yellow slime mould (Fuligo septica) growing on a rotting pine stump, Surrey, England, April.

Alex Hyde / Knotted / Egg Wrack seaweed (Ascophyllum nodosum) growing in middle shore zone, exposed at low tide. Isle of Mull, Scotland, UK. June.

Alex Hyde / Knotted / Egg Wrack seaweed (Ascophyllum nodosum) growing in middle shore zone, exposed at low tide. Isle of Mull, Scotland, UK. June.

Pascal Kobeh / Saddleback anemonefish (Amphiprion polymnus) ventilating its eggs near a Haddon's sea anemone (Stichodactyla haddoni), Manado, Indonesia. Sulawesi Sea.

Alex Mustard / Group of Saddleback anemonefish (Amphiprion polymnus) guard clutch of eggs, laid on stone near the base of anemone. Dauin, Dumaguete, Negros, Philippines. Bohol Sea, Tropical West Pacific Ocean.

Will Watson / Sulphur-yellow slime mould (Fuligo septica), on dead wood, Llanerchaeron National Trust, Ceredigion, Wales, UK, August.

Jussi Murtosaari / Swallowtail (Papilio machaon) egg or ovum, central Finland, June.

Nick Upton / Egg masses of Common whelk (Buccinum undatum) washed up on high water mark alongside dried out Bladder wrack fronds (Fucus vesiculosus), Rhossili, The Gower peninsula, Wales, UK, June.

Alex Mustard / A male Lumpsucker (Cyclopterus lumpus) guarding his yellow egg mass. Gulen, Bergen, Norway. North East Atlantic Ocean.

Alex Mustard / Male Yellow-headed jawfish (Opistognathus aurifrons) blows out the clutch of eggs he is incubating in his mouth to oxygenate them. East End, Grand Cayman, Cayman Islands, British West Indies. Caribbea...

Franco Banfi / Catshark egg (Scyliorhinus sp) on Red sea fan (Paramuricea clavata) Stupiste In dive site, Vis Island, Croatia, Adriatic Sea, Mediterranean

Alex Hyde / Dog Vomit / Scrambled Egg Slime Mould (Fuligo septica var. septica), a species of plasmodial slime mould (Myxomycetes class). Found on deciduous woodland floor. Peak District National Park, Derbyshire...

Alex Hyde / Dog Vomit / Scrambled Egg Slime Mould (Fuligo septica var. septica), a species of plasmodial slime mould (Myxomycetes class). Found on deciduous woodland floor. Peak District National Park, Derbyshire...

Pete Oxford / Yellow-spotted Amazon River Turtle (Podocnemis unifilis) eggs for sale -illegally harvested from Yasuni National Park, Pompeya Market, Amazon, Ecuador

Pete Oxford / Yellow-spotted Amazon River Turtle (Podocnemis unifilis) eggs for sale - illegally harvested from Yasuni National Park, Pompeya Market, Amazon, Ecuador

Nick Garbutt / Egg of Giraffe-necked weevil (Trachelophorus giraffa) laid inside the leaf of favourite host tree (Dichaetanthera cordifolia), Ranomafana National Park, eastern Madagascar, November

Juergen Freund / Squid (Teuthoidea) egg cases on the sand. Lembeh Strait, North Sulawesi, Indonesia.

Robert Thompson / Flowers of tan / Dog vomit / Scrambled egg slime mould (Fuligo septica) on pine needles, Tollymore Forest, County Down, Northern Ireland, UK, October

Adrian Davies / Slime Mould {Fuligo septica} sometimes called scrambled egg mould, or dog vomit fungus, UK

Silvia Reiche / Oldworld Swallowtail (Papilio machaon) egg, Hoogeloon, Noord-Brabant, Netherlands

Philippe Clement / Dog vomit / Scrambled egg slime mould (Fuligo septica), Belgium

Philippe Clement / Dog vomit / Scrambled egg slime mould (Fuligo septica), Belgium

Jouan & Rius / Poached egg daisy (Polycalymma stuartii) flowering on sand desert, Central Australia, Northern Territory, Australia

Jouan & Rius / Poached egg daisy (Polycalymma stuartii) flowering on sand desert, Central Australia, Northern Territory, Australia

Ingo Arndt / Swallowtail (Papilio sp) butterfly egg attached to the underside of leaf, Germany

Nature Production / Larva of Chinese Yellow Swallowtail Butterfly {Papilio xuthus} recently hatched, feeding on egg shell, Japan

Willem Kolvoort / Red eyed damselflies (Erythromma najas) mating and laying eggs in stem of Yellow water lily (Nuphar lutea) Lake Naarden, Holland

Jose B. Ruiz / Yellow legged gull {Larus michahellis} chick hatching from egg, Santa Pola Saltmarshes, Alicante, Spain

Pete Oxford / Yellow foot tortoise baby showing egg tooth {Geochelone denticulata} Amazonia, Ecuador

Jan Vermeer / Porcelain Mushroom (Oudemansiella mucida) detail of gills on the underside, Europe

Pete Oxford / Yellow-footed Tortoise (Geochelone denticulata) hatchling showing egg-tooth which is used to break out of egg, tropical rainforest, Ecuador

Michael & Patricia Fogden / Golden Toad (Bufo periglenes) pair spawning in temporary pool, Monteverde Cloud Forest Reserve, Costa Rica

Nigel Cattlin / Harlequin ladybird (Harmonia axyridis) eggs on a strawberry leaf Berkshire, England, UK.

Nigel Cattlin / Crab apple, (Malus 'John Downie'), with red, orange-yellow ovoid fruit on the tree, Berkshire, August

Nigel Cattlin / Yellow stem borer (Scirpophaga incertulas) pest moth egg mass on a Rice (Oryza sativa) stem, luzon, Philippines

Pete Oxford / Nudibranch (Aegires gardineri) pair laying eggs, Raja Ampat Islands, Indonesia