Once adult frogs reach maturity, they will assemble at a water source such as a pond or stream to breed. The black strands are eggs released into open water minutes after birth. Once at the breeding ground, male frogs call to attract a mate, collectively becoming a chorus of frogs. The male and female frogs then undergo amplexus. This involves the male mounting the female and gripping her tightly. Fertilization is external: the egg and sperm meet outside of the body. The female releases her eggs, which the male frog covers with a sperm solution. The eggs then swell and develop a protective coating.
Most temperate species of frogs reproduce between late autumn and early spring. In the UK, most common frog populations produce frogspawn in February, although there is wide variation in timing. Water temperatures at this time of year are relatively low, typically between four and 10 degrees Celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures.
Source: en.wikipedia.org/wiki/Frog - 20.05.2010
In reality this Frog Baby has the size of a fingernail!