The influence of temperature on the development of a Mendelian character

DeVries and Johannsen hold that, in the absence of mutation, selection can do nothjng but sort out from a population characteristics already existing.According to this conception, any population may be made up of a series of forms, and this series may be broken up into smaller groups by selection, but the limit of variability can not be transcended.The most extreme individuals in a race produced by such a sorting-out process are no more extreme than the most extreme in the heterogeneous population.Recently Castle and others have endeavored to show that selection may affect the degree of development of the character selected.