Wallace and Bates discussed the idea of an expedition to the Amazon. The plan was to defray expenses by sending specimens back to London, where an agent would sell them for a commission. Also, for the travellers to ""gather facts towards solving the problem of the origin of species"", as Wallace put it in a letter to Bates. The two friends, who were both by now experienced amateur entomologists, met in London to prepare themselves by viewing South American plants and animals in the main collections.