Evolution quotes

Evolution and phylogeny.—Evolution is the process and phylogeny the record of descent. Phylogeny is thus the measure of relationship, and is to be expressed in terms of community of ancestry; hence, if relationship is to express evolution adequately, it must take account of each change, from the branch to the variad. It must arrange these in their proper phylogenetic order, and denote them by such terms as will clearly indicate their fixed phylogenetic position. This has long been done for the most part, but the fact has too often been overlooked that the sequence of changes is fixed in practically all regions of intense evolution. The genus exhibits lines of evolution expressed in the sections, and the species shows more recent changes marked by variads. … A natural classification must maintain as well as reveal the different degrees of relationship ‘as expressions of different stages of evolution, and it can do this most accurately with genera, sections, species, and variads, where the lines of evolution are still in a condition conducive to experimental study. [Hall, Harvey Monroe and Clements, Frederick E. (1923), The phylogenetic method in taxonomy; the North American species of Artemisia, Chrysothamnus, and Atriplex (On verso of t.-p.: Carnegie institution of Washington. Publication no. 326; Washington,: The Carnegie institution of Washington) 1 l., iv, 355, p 5.]