Fig. 8. Section through the sympathetic ganglion of a Scyllium embryo between stages M and N, shewing the connecting trunk between the suprarenal body and the spinal nerve (_spn_), and the appearance of an indication in the ganglion of a portion more directly connected with the nerve. Zeiss D, ocul. 2. Fig. 9. Section through one of the anterior sympathetic ganglia of an embryo of stage Q, shewing its division into a true ganglionic portion (_syg_), and a suprarenal body (_sr_). Zeiss C, ocul. 2. EXPLANATION OF PLATES 20 AND 21. (X. p. 479.) COMPLETE LIST OF REFERENCE LETTERS. _amg._ Accessory Malpighian body. _cav._ Cardinal vein. _ge._ Germinal epithelium. _k._ True kidney. _l.c._ Longitudinal canal of the Wolffian body connected with vasa efferentia. _mg._ Malpighian body. _nt._ Network and central canal at the base of the testis. _o._ External aperture of urinal cloaca. _od._ Oviduct or Müllerian duct of the female. _od´._ Müllerian duct of the male. _ou._ Openings of ureters in Wolffian duct in the female (fig. 3). _pmg._ Primary Malpighian body. _px._ Growth from vesicle at the end of a segmental tube to join the collecting tube of the preceding segment. _rst._ Rudimentary segmental tube. _ru._ Ureter commencing to be formed. _sb._ Seminal bladder. _sd._ Segmental duct. _st._ Segmental tube. _sto._ Opening of segmental tube into body-cavity. _sur._ Suprarenal body. _t._ Testis. _u._ Ureters. _ve._ Vas efferens. _wb._ Wolffian body. _wd._ Wolffian duct. PLATE 20. Fig. 1. Diagrammatic representation of excretory organs on one side of a male Scyllium canicula, natural size. Fig. 2. Diagrammatic representation of the kidney proper on one side of a female Scyllium canicula, natural size, shewing the ducts of the kidney and the dilated portion of the Wolffian duct. Fig. 3. Opening of the ureters into the Wolffian duct of a female Scyllium canicula. The figure represents the Wolffian ducts (_wd_) with ventral portion removed so as to expose their inner surface, and shews the junction of the two W. ducts to form the common urinal cloaca, the single external opening of this (_o_), and openings of ureters into one Wolffian duct (_ou_). Fig. 4. Anterior extremity of Wolffian body of a young male Scyllium canicula shewing the vasa efferentia and their connection with the kidneys and the testis. The vasa efferentia and longitudinal canal are coloured to render them distinct. They are intended to be continuous with the uncoloured coils of the Wolffian body, though this connection has not been very successfully rendered by the artist.