Influences interfering with the free development of the anterior or posterior border of the parietal bone could only deflect upwards or downwards the marginal end of an incomplete parietal suture, or, at most, in a case of a short suture, render it oblique or curved in its entirety. No pathological condition, unless it were accompanied by a fracture, could extend even a deflected antero-posterior incomplete division to any of the borders of the bone. There are, it seems to me, only three possible ways in which an oblique suture, extending between any two borders of the parietal bone, can be produced. In the first case the oblique suture, or rather a suture-like formation, may be the effect of an early fracture. A fracture produced in adult life is generally recognizable as such; but a fracture dating from earlier stages of life, produced before the growth of the bone has ceased, may, if not entirely obliterated, present more or less the characteristics of a suture. I have seen several skulls where a division in the parietal bone or the temporal squama presented at the same time features of a fracture and suture; in one or two of these cases so much so, that it was and still is impossible for me to decide exactly which of the two conditions I had before me. Gruber describes one such case[12] as an instance of an oblique parietal suture, while Hyrtl and Ranke both consider this case as one with an acquired division. To differentiate a congenital real oblique suture from a division which is the result of a fracture, we must be guided largely by the situation, form, and serration of the division, and the condition of the surrounding bones, especially that of the opposite parietal. A straight course, ending with one extremity in or near the middle of the anterior or posterior border of the parietal, a complex serration, no continuity of the division on the neighboring bones, and particularly a co-existence of an allied or similar division on the opposite parietal,--all favor the conclusion that the division under consideration is a real congenital suture, and not the result of a fracture. In the second case there are reasons for believing that an oblique suture of the parietal bone can originate in the same way as the horizontal one, namely, through a persistence of the original separation between the two centres from which the bone is developed, and a co-existent difference in the relative position or the relative growth of the two centres. It is in this connection that the above-described division in the parietals of the chimpanzee will prove of value.