II URINO-GENITAL ORGANS 5 I 



appearance as if the single duct itself were dilated in the greater 

 part of its length ; hence the occasional name of vesicula serainalis. 

 Such means of storing the sperma enable the latter to he ejected 

 suddenly in great quantities. 



In Bomhinator (6) some of the most anterior seminal canals do 

 not perforate the kidney, hut run over it superficially and open 

 directly into a branch of Leydig's duct. This l:)ranch, no doul )t 

 equivalent to a number of segmental canals which have lost 

 their uriniferous function, is curved round the upper end of the 

 permanent kidney, while its forward continuation, ending blindly, 

 is the remnant of its former head ward extension. This arrange- 

 ment of Bomhinator is carried further in Discoglossus (7). The 

 testis conveys its sperma through a wide duct directly into Leydig's 

 canal, without interfering with the kidney, and all the testicular 

 efferent network is lost. The anterior end of Leydig's duct 

 still extends headwards ; its middle portion acts solely as a vas 

 deferens, while the lower portion still behaves like a typical 

 segmental duct, convepng both sperma and urine. Lastly, in 

 Alytes (8) the functional division of the old segmental duct has been 

 carried to an extreme. The kidney is drained hy one canal only, 

 now a true ureter, and this is of course produced by a consolida- 

 tion of the multiple exclusively uriniferous canals of the lower 

 half of the kidney. The whole of the segmental duct is now 

 in the service of the testis, and near its junction with the ureter 

 it forms a large diverticulum or true vesicula seminalis. 



Eemnants of oviducts, or Miillerian ducts, are common in the 

 male Anura ; they are best developed in Bufo, much reduced, 

 and individually absent, in Rana. In Bomljinator each duct is 

 restricted to its upper or abdominal portion, and is attached to 

 the A^estigial headward extension of Leydig's duct. Lastly in JJis- 

 coglossus and in Alytes all traces of oviducts seem to have vanished, 

 at least in the adult males. 



It is interesting to note that in the arrangement of the urino- 

 genital ducts the Discoglossidae are the most advanced of all 

 Amphibia, instead of showing the most primitive conditions. 

 This is rather unexpected, but is paralleled by the epichordal 

 type of the vertebral column. 



The oviducts of the Apoda and Urodela remain more or less 

 straight : in the viviparous species they form uterus-like dilata- 

 tions. In the Anura they become greatly elongated during the 



