Charles Darwin studied for eight years to write a 4-volume work about which creatures?

Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist and geologist, best known for his contributions to the science of evolution. He established that all species of life have descended over time from common ancestors.

Darwin’s interest in Cirripedia, a class of marine arthropods, was first piqued by the discovery of an odd burrowing barnacle, which he later named “Mr. Arthrobalanus," while he was aboard the HMS Beagle. Darwin dissected, classified, and wrote about barnacles on a daily basis from 1846 to 1854. Ultimately, Darwin's deep and focused research on barnacles resulted in the publication of four serious monographs, which established him as a major figure in the British zoological community. (Darwin's earlier geological publications had already established him as a man of scientific merit).