This contains four original papers that are fundamental to our understanding of modern biology, including Gregor Mendel's Experiments in Plant Hybridization, Alfred Russel Wallace's On the Tendency of Varieties to Depart Indefinitely from the Original Type, Thomas H. Huxley's initial review of Darwin's On Origin of Species, and James Watson and Francis Crick's paper groundbreaking paper Molecular Structure of Nucleic Acids.