EXCRETORY ORGANS IN THE ADULT. 481 



long, the two glands together measured 8 centimetres and the 

 kidney proper only 3^. In the male the Wolffian bodies ex- 

 tend somewhat further forwards than in the female. Leaving 

 the finer details of the glands for subsequent treatment, I pass 

 at once to their ducts. These differ slightly in the two sexes, 

 so that it will be more convenient to take the male and female 

 separately. 



A partly diagrammatic representation of the kidney and 

 Wolffian body of the male is given on PL 20, fig. i. The se- 

 cretion of the Wolffian body is carried off by a duct, the Wolffian 

 duct (w. d.), which lies on the ventral surface of the gland, and 

 receives a separate ductule from each segment (PI. 20, fig. 5). 

 The main function of the Wolffian duct in the male is, how- 

 ever, that of a vas deferens. The testicular products are brought 

 to it through the coils of the anterior segments of the Wolffian 

 body by a number of vasa efferentia, the arrangement of which 

 is treated of on pp. 487, 488. The section of the Wolffian duct 

 which overlies the Wolffian body is much contorted, and in 

 adult individuals at the generative period enormously so. The 

 duct often presents one or two contortions beyond the hind end 

 of the Wolffian body, but in the normal condition takes a 

 straight course from this point to the unpaired urinogenital 

 cloaca, into which it falls independently of its fellow of the 

 opposite side. It receives no feeders from the kidney proper. 



The excretion of the kidney proper is carried off not by a 

 single duct, but by a series of more or less independent ducts, 

 which, in accordance with Prof. Semper's nomenclature, will be 

 spoken of as ureters. These are very minute, and their in- 

 vestigation requires some care. I have reason, from my ex- 

 aminations of this and other species of Elasmobranchs, to be- 

 lieve that they are, moreover, subject to considerable variations, 

 and the following description applies to a definite individual. 

 Nine or possibly ten distinct ureters, whose arrangement is 

 diagrammatically represented in fig. I, PL 20, were present on 

 each side. It will be noticed that, whereas the five hindermost 

 are distinct till close to their openings into the urinogenital 

 cloaca, the four anterior ones appear to unite at once into a 

 single duct, but are probably only bound up in a common 

 sheath. The ureters fall into the common urinogenital cloaca, 



