335 



It appears therefore, that the efferent ducts, which are doubtless, 

 as in Plagiostomes, derivatives of certain of the embryonic mesonephric 

 tubules, have become completely emancipated from the main body of 

 the mesonephros, and that probably one of them only, serving as a 

 collector, remains in connexion with the spermiduct (Figs. 1 and 3). 



From the embryological point of view there is, therefore, a 

 representative of a "Geschlechtsniere", but the actual mesonephros of 

 the adult does not include a sexual portion ("cranial zone") as is 



v.ef.col' 



Fig. 3. Fig. 4. 



Fig. 3. Longitudinal vertical section through region a in plane b of Fig. 1 

 (X about 10). c.t. connective tissue; ms. mesonephric tubules; ms'. ducts of mesonephric 

 tubules which open into spermiduct; sp.d. spermiduct containing spermatophores; sp.d'. 

 spermiduct containing loose sperms; v.ef.col, longitudinal collector of efferent ducts. 



Fig. 4. Transverse section in region c of Fig. 1 (X about 6). ms. mesonephric 

 tubules; sp.d. spermiduct containing spermatophores; sp.d'. spermiduct containing loose 

 sperms ; v.ef.col'. region at which the collector becomes continuous with the spermiduct. 



usually the case in adult Plagiostomes, It must however be borne in 

 mind that most of the observations on the mesonephros of Selachians 

 have been made on embryonic material, and that the later stages have 

 not in all cases been followed^). 



1) In connexion with the contradictory statements relating to the 

 vasa efferentia in Pristiurus by Semper, ("Das Urogenitalsystem der 



