Dr. Romanes on Physiological Selection

Abstract

As Dr. Romanes now declares that the essence of his theory of physiological selection is “that some amount of infertility characterizes the distinct varieties which are in process of differentiation into species,” and that the occurrence of infertility among the members of an undifferentiated species is secondary and comparatively unimportant, I ask leave to quote one or two more of his original statements, in addition to the four emphatic passages quoted in my communication of November 27.