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Developing frog egg. Light micrograph of a transverse section through a developing egg laid by a common frog (Rana temporaria). The egg has reached the early neurula stage. The neural plate (purple bottom centre) is present just before folding to form the neural tube. Several germ layers (tissue types) have also formed. The embryo will eventually develop into a tadpole, and then into a fully formed adult frog. The whole process from egg to adult takes around 16 weeks. The embryo development takes place at the frogspawn stages, and it takes around 10 days for the tadpoles to form from the fertilised eggs. Magnification: x13 when printed at 10 centimetres wide.