{768} separately. The enlargement of the eye, like the modification in form and number of the teeth, is a separate phenomenon, which supplements but in no way contradicts our general comparison of the skulls taken in their entirety.
Before we leave the Perissodactyla and their allies, let us look a little more closely into the case of the horse and its immediate relations or ancestors, doing so with the help of a set of diagrams which I again owe to Mr Gerard Heilmann. Here we start afresh, with the skull (Fig. 402, A ) of Hyracotherium (or Eohippus ), inscribed in a simple Cartesian network. At the other end of