DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Frog embryo, blastula stage, light micrograph. This is an embryo of a pond frog (Rana), in longitudinal section, at the blastula stage. Many small cells surround a fluid-filled cavity (the blastocoel). 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. For a sequence of frog embryo stages, see images C012/2756-2760. Magnification: x13 when printed at 10 centimetres tall.
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