The following paper is the result of investigations which were begun several years ago, under the inspiration of Huxley’s prophecy that paleontology, when properly interrogated, would reveal to us the true laws of evolution. I have at last succeeded in getting together a long series of samples of a single race inhabiting successively the same region; have subjected them to minute measurement, and by reducing their morphologic characters to mathematical terms have enabled them to speak for themselves regarding at least one of the essential laws of evolution, the law of fluctuating variation.
One of the greatest difficulties met with in making such an investigation is the practice of using extremely vague and elastic terms in describing the specific characters of fossil organisms. Generic characters are in many cases made more definite by the fact that the diagnostic characters are either present or absent . . .