EXPLANATION OF PLATE XIX. 



Complete list of reference letters. 



a.mg. accessory Malpighian body. k. true kidney. 



I. c. longitudinal canal of the Wolffian body connected with vasa 



efferentia. 



nt. network and central canal at the base of the testis. 



0. external aperture of urinal cloaca. 



0. u. openings of ureters in Wolffian duct in the female (Fig. 3). 



2). ing. primary Malpighian body. 



r. St. rudimentary segmental tube. 



s. h. seminal bladder. st. segmental tube. 



st.o. opening of segmental tube into body-cavity. 



t. testis, u. ureters. v. e. vas efferens. 



ic. b. Vrolffian body. 2€. cl. Wolffian duct. 



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 {ic.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 [oil). 



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 secondai7 Malpighian body of preceding segment. It also shews one seg- 

 mental 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. 



