The occasional persistence of the separation between the two original segments of the parietal bone is sufficiently demonstrated by the presence of the complete horizontal parietal suture. Differences in the relative position of these segments can be observed in a limited degree in Ranke's illustrations of embryos, before referred to; it can be deduced from such cases as the two of Hyrtl,[13] in which the division of the parietal was directed from the upper portion of the anterior to the lower portion of the posterior border of the bone. The most pronounced change in the position of these centres may be witnessed in cases where the parietal bone shows a perfect vertical instead of a horizontal suture. Such cases have been referred to before, and I presented at the meeting of the Association of American Anatomists, in 1899, several such examples, found by me in skulls of monkeys in Professor Huntington's anatomical collection in the Medical Department of Columbia University. One of these specimens is shown in the accompanying illustration (Fig. 5). A difference in the relative growth of the two centres of the parietal bone is well shown in the difference of size between the inferior and superior portions of the parietal in cases of the complete horizontal suture in the same. In the majority of such cases on record the superior portion is larger, particularly anteriorly, than the inferior; so much so, that that condition seems to be the typical one. The difference in the size of the two portions of the parietal, and in their relative anterior and posterior height, is most pronounced in one of Gruber's cases,[14] where the "parietal suture" begins only 10 mm. above the pterion, and ends 40 mm. above the asterion. In Dorsey's case[15] the lower portion of the divided parietal is 12 mm. higher than the upper. The same condition as is found in Gruber's case, here mentioned, exists in the almost identical left division of the second case of Putnam, of which I have a photograph in my hands. A somewhat similar excess of the posterior over the anterior part of the lower severed portion of the parietal can also be seen in the illustrations of the cases of Tarin, Lucae, and Turner (Admiralty Islands skull). In Calori's interesting case[16] there is a decided excess of the lower portion of the divided parietal in its posterior portion on the left and in its anterior portion on the right side. [Illustration: Fig. 5. _Macacus rhesus_ (Medical Department, Columbia University), showing a Complete Division of the Right Parietal Bone in a Vertical Direction.]