The body cavity is formed of four compartments—one central, two lateral, and a pericardial (Fig. 14, D). The former is by far the largest, and contains the alimentary tract, the generative organs, and the slime glands. It is lined by a delicate endothelial layer, and is not divided into compartments nor traversed by muscular fibres. The lateral divisions are much smaller than the central, and are shut off from it by the inner transverse band of muscles. They are almost entirely filled with the nerve-cord and salivary gland in front and with the nerve-cord alone behind, and their lumen is broken up by muscular bands. They further contain the nephridia. They are prolonged into the feet, as is the embryonic body cavity of most Arthropoda. The pericardium contains a peculiar cellular tissue, probably, as suggested by Moseley, equivalent to the fat-bodies of insects. NEPHRIDIA. In _Peripatus capensis_ nephridia are present in all the legs. In all of them (except the first three) the following parts may be recognised (Fig. 11):— (1) A vesicular portion opening to the exterior on the ventral surface of the legs by a narrow passage. (2) A coiled portion, which is again subdivided into several sections. (3) A section with closely packed nuclei ending by a somewhat enlarged opening. (4) The terminal portion, which consists of a thin-walled vesicle. The last twelve pairs of these organs are all constructed in a very similar manner, while the two pairs situated in the fourth and fifth pairs of legs are considerably larger than those behind, and are in some respects very differently constituted.