Fig. 5. Part of the Wolffian body of a nearly ripe male embryo of Scyllium canicula as a transparent object. Zeiss a a, ocul. 3. The figure shews two segmental tubes opening into the body-cavity and connected with a primary Malpighian body, and also, by a fibrous connection, with a secondary Malpighian body of the preceding segment. It also shews one segmental tube (_rst_) imperfectly connected with the accessory Malpighian body of the preceding segment of the kidney. The coils of the kidney are represented somewhat diagrammatically. Fig. 6. Vasa efferentia of a male embryo of Scyllium canicula eight centimetres in length. Zeiss a a, ocul. 2. There are seen to be at the least six and possibly seven distinct vasa going to as many segments of the Wolffian body and connected with a longitudinal canal in the base of the testis. They were probably also connected with a longitudinal canal in the Wolffian body, but this could not be clearly made out. Fig. 7. The anterior four vasa efferentia of a nearly ripe embryo. Connected with the foremost one is seen a body which looks like the remnant of a segmental tube and its opening (_rst?_). Fig. 8. Testis and anterior part of Wolffian body of an embryo of Squatina vulgaris. The figure is intended to illustrate the arrangement of the vasa efferentia. There are five of these connected with a longitudinal canal in the base of the testis, and with another longitudinal canal in the Wolffian body. From the second longitudinal canal there pass off four ducts to as many Malpighian bodies. Through the Malpighian bodies these ducts are continuous with the several coils of the Wolffian body, and so eventually with the Wolffian duct. Close to the hindermost vas efferens is seen a body which resembles a rudimentary segmental tube (_rst?_). PLATE 21. Figs. 1A, 1B, 1C, 1D. Four sections from a female Scyllium canicula of a stage between M and N through the part where the segmental duct becomes split into Wolffian duct and oviduct. Zeiss B, ocul. 2. 1A is the foremost section. The sections shew that the oviduct arises as a thickening on the under surface of the segmental duct into which at the utmost a very narrow prolongation of the lumen of the segmental duct is carried. The small size of the lumen of the Wolffian duct in the foremost section is due to the section passing through nearly its anterior blind extremity. Fig. 2. Section close to the junction of the Wolffian duct and oviduct in a female embryo of Scyllium canicula belonging to stage N. Zeiss B, ocul. 2. The section represented shews that in some instances the formation of the oviduct and Wolffian duct is accompanied by a division of the lumen of the segmental duct into two not very unequal parts. Figs. 3A, 3B, 3C. Three sections illustrating the formation of a ureter in a female embryo belonging to stage N. Zeiss B, ocul. 2. 3A is the foremost section.