Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 18 days development, the tadpoles are fully developed and ready to hatch, Ecuador. Endangered. (non-ex)

Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Morley Read / Developing embryo of the Ecuadorian monkey frog (Phyllomedusa ecuatoriana), showing heart beating and blood flowing, Morona Santiago Province, Ecuador, (non-ex)

Morley Read / Close-up of an Amazon leaf frog (Cruziohyla Craspedopus) tadpole developing in egg, Ecuador. (non-ex)

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

Alastair MacEwen / Time-lapse of toadspawn from a Common toad (Bufo bufo) developing, emerging and feeding on nutrient jelly, Somerset, England, UK, April.

Ingo Arndt / Mass of Sea trout (Salmo trutta trutta) eggs, with embryos visible, Europe.

Doug Wechsler / Horseshoe crab (Limulus polyphemus) embryos, Delaware Bay, New Jersey, USA, June.

Solvin Zankl / Sorting Common fruit fly (Drosophila melanogaster) laboratory culture embryos for DNA injection at the Vienna Drosophila RNAi Center, Institute for Molecular Pathology, Austria.

Jane Burton / Common Frog (Rana temporaria) tadpoles developing in spawn

Fabio Liverani / Yellow bellied toad - eggs with developing embryos, Italy. Life cycle sequence 2

Morley Read / Close-up of Leaf frog (Cruziohyla craspedopus) tadpoles developing within an egg membrane, blood is circulating in the gills. Pastaza Province, Ecuador. (non-ex)