I have still to add a few remarks on the subject touched on in the footnote at page 31. The view there referred to was discussed by Professor Scott before in an article published in the _American Journal of Science_, Vol. XLVIII., for November, 1894, entitled "On Variations and Mutations." Following the precedent of Waagen and Neumayr, Scott sharply discriminates between the inconstant vacillating variations which it is supposed [?] produce simultaneously occurring "varieties," and "mutations," or the successively evolved _time_-variations of a phylum, which constitute the stages of phyletic development. The facts on which this view is based are those already {73} adduced in the text--the _Zielstrebigkeit_ (to use K. E. von Baer's phraseology) displayed in the visible paleontological development, the directness of advance of the modifications to a final "goal." "The direct, unswerving way in which development proceeds, however slowly, is not suggestive of many trials and failures in all directions save one." And again, "The march of transformation is the resultant of forces both internal and external which operate in a _definite manner_ upon a changeable organism and similarly affect _large numbers of individuals_." The two points which I have here italicised are actually the facts which separate phylogenetic from common individual variation: the definite _manner_ of the change, repeated again and again without modification, and its occurrence in a _large number of individuals_.