1. The influence of peritoneal adhesions established during the descent of the caecum from the subhepatic position to the iliac fossa. 2. The inherent curve of the caecal pouch. 3. The subsequent alterations in the caliber of the intestine and the unequal development of the pouch leading to the formation of the types of adult caeca above considered. In determining the causes which lead to the establishment of any given position of the appendix all three of the factors above enumerated must be taken into account, although their influence is not exerted in every case to an equal degree. We have seen that normally, after completed rotation of the intestine, the caecum with the appendix and the beginning of the colon are lodged in the upper and right part of the abdomen, below the liver and in contact with the prerenal parietal peritoneum (schema, Figs. 493, 502). During the subsequent stages the caecum descends into the right iliac fossa, thus producing the ascending colon. It is immaterial whether this change in position is regarded as an actual descent of the pouch over the ventral surface of the right kidney, which seems more probable, or as a growing away from the iliac region of the remainder of the abdominal wall, with a concomitant relative reduction in the size of the liver, producing a relatively lower position of the caecum, or as a combination of these processes. In either case during this period the dorsal surface of the ascending colon and mesocolon normally becomes adherent to the dorsal parietal peritoneum, connective tissue developing between the opposed serous areas and leading to the usual fixation of the ascending colon and obliteration of the free ascending mesocolon. If this process of adhesion is inaugurated at an early stage, _i. e._, before the descent of the caecum has been accomplished, it will act as a drag on the dorsal surface of the colic tube during the subsequent change in position, which carries the caecum downward into the iliac fossa. This leads to a backward bend of the caecum and appendix which parts will in the ventral view appear under cover of the protruding free ventral and lateral walls of the colon. Hence in many late embryos and foetus at term the lowest point of the large intestine in the right iliac fossa is formed by the proximal part of the caecum or by the adjacent segment of the colon, while the original termination of the pouch, with the root of the appendix, is turned backward and upward, and, as we have seen, by reason of the inherent shape of the pouch, also to the left, carrying the beginning of the appendix frequently behind the terminal ileum and the ileo-colic junction.