From the first the connective-tissue cells around the hypoblastic epithelium of the alimentary tract are fairly numerous (Pl. 11, fig. 8), and by the close of this period become concentrically arranged round the intestinal epithelium, though not divided into distinct layers. A special aggregation of them is present in the hollow of the rudimentary spiral valve. Behind the anal region the two layers of the mesoblast (somatic and splanchnic) completely fuse during stage K, and form a mass of stellate cells in which no distinction into two layers can be detected (Pl. 11, figs. 9_c_, 9_d_). The alimentary canal, which at first lies close below the aorta, becomes during this period gradually carried further and further from this, remaining however attached to the roof of the body-cavity by a thin layer of the mesoblast of the splanchnopleure formed of an epithelium on each side, and a few interposed connective-tissue cells. This is the mesentery, which by the close of stage K is of considerable length in the region of the stomach, though shorter elsewhere. * * * * * The above account of the protovertebræ and body-cavity applies solely to the genera Pristiurus and Scyllium. The changes of these parts in Torpedo only differ from those of Pristiurus in unimportant though fairly noticeable details. Without entering into any full description of these it may be pointed out that both the true body-cavity and its continuations into the protovertebræ appear later in Torpedo than in Pristiurus and Scyllium. In some cases even the muscle-plates become definitely separated and independent before the true body-cavity has appeared. As a result of this the primitive continuity of the body-cavity and cavity of the muscle-plates becomes to a certain extent masked, though its presence may easily be detected by the obvious continuity which at first exists between the somatic and splanchnic layers of mesoblast and the two layers of the muscle-plate. In the muscle-plate itself the chief point to be noticed is the fact that the earlier formed bands of muscles (_mp´_) arise very much later, and are less conspicuous, in Torpedo than in the genera first described. They are however present and functional. The anatomical relations of the body-cavity itself are precisely the same in Torpedo as in Pristiurus and Scyllium, and the pericardial cavity becomes separated from the peritoneal in the same way in all the genera; the two lateral canals connecting the two cavities being also present in all the three genera. The two independent parietal plates of mesoblast of the posterior parts of the body have ventrally a swollen edge, as in Pristiurus, and in this a cavity appears which forms a posterior continuation of the true body-cavity.