5l8 DEVELOPMENT OF ELASMOBRANCH FISHES. 



EXPLANATION OF PLATES 20 AND 21. 



COMPLETE LIST OF REFERENCE LETTERS. 



a mg. Accessory Malpighian body. cav. Cardinal vein. ge. Germinal epithelium. 

 k. True kidney. /. 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 Miillerian duct 

 of the female, od' . Miillerian 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, r st. Rudimentary segmental tube. tu. Ureter commencing to be formed. 

 s b. Seminal bladder, s d. Segmental duct, s t. Segmental tube, st o. Opening of 

 segmental tube into body-cavity, sur. Suprarenal body. t. Testis. it. Ureters. 

 ve. Vas efferens. w b. Wolffian body, w d. Wolffian duct. 



PLATE 20. 



Fig. r. 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 por- 

 tion 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 (w d) 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. 



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 (r st) 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 iri 

 the Wolffian body, but this could not be clearly made out. 



