 For example, natural variation is employed by Darwin in chapter two of the Origin to break down the distinction between species and varieties as these concepts were commonly employed in the practical taxonomic literature. The arbitrariness apparent in making distinctions, particularly in plants and invertebrates, meant that such species were only what “naturalists having sound judgment and wide experience” defined them to be (Origin 1859: 47). These arguments form the basis for claims by his contemporaries that Darwin was a species “nominalist”, who defined species only as conventional and convenient divisions of a continuum of individuals.