Nuptial pad

A nuptial pad (also known as thumb pad, or nuptial excrescence) is a thick piece of flesh on the front feet of some frogs and salamanders. Only adult male animals have this pad.
The nuptial pad is a gland. It is a secondary sex characteristic. The male animals use the nuptual pad to hold on to females when they mate, but it does not make or move sperm itself. Some animals use their nuptial pads to fight each other.
Historical background.
Austrian biologist Paul Kammerer looked at midwife toads' nuptial pads. He believed in Lamarckian evolution. This means he thought that the male frogs' pads got bigger in their own lifetimes, and then they passed the big pads on to their young after that. But this is not how evolution truly works.
Examples.
Many amphibian species grow nuptial pads for mating. For example, the rough-skinned newt ("Taricha granulosa") does.