The ventral caecal branch of the ileo-colic artery is slightly developed, (1) as a small vessel descending in an epiploic fold over the ventral surface of the ileo-colic junction as far as the root of the appendix. The intermediate non-vascular fold (3) is well marked, measuring 2.9 cm. in length, extending from the free border of the terminal ileum to the caecum and appendix and crossing over the well-developed dorsal vascular fold (2), which descends, as the appendicular mesenterolium, to the tip of the appendix, carrying the dorsal artery. In studying the conditions presented by this specimen, it is not difficult to trace the analogous structures in the caeca of _Cercopithecus_, _Ateles_ and _Mycetes_. The same vascular and non-vascular serous reduplications are found passing between the ileum and caecum. In accordance with the type presented by _Cercopithecus_ the ventral artery is much reduced and runs in a short serous fold loaded with epiploic appendages. The dorsal artery, on the other hand, is well developed and the intermediate non-vascular fold is distinct. In their relative arrangement these folds follow the _Ateles_ type. The dorsal vascular fold forms the true mesentery of the appendix, and, although close to and crossed by the intermediate non-vascular reduplication, remains still quite separable and distinct from the same; consequently the lower limit of the usual posterior ileo-caecal fossa, produced by the fusion of the dorsal vascular and the intermediate non-vascular fold, is absent. A very perfect illustration of this type of the human ileo-caecal fold is presented by the preparation of _Gorilla savagei_ shown in Fig. 457. The ventral fold and artery appear reduced in this animal. The dorsal vascular fold forms a broad triangular plate of serous membrane carrying the dorsal artery in its free border and extending to the tip of the appendix. The intermediate non-vascular fold is narrow but distinct, continued for a considerable distance along the ileum, opposite to the attached border, but only for a short extent along the left border of the caecum below the ileo-colic junction. It crosses the ventral surface of the broad dorsal vascular fold in passing to the caecum, but remains entirely free and is not adherent to the same.