826 STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 



Judging from the structure of the adult genital ducts of other 

 Ganoids they must also be developed only from the posterior 

 part of the segmental duct, and this peculiarity so struck one of 

 us that in a previous paper 1 the suggestion was put forward that 

 the true Ganoid genital ducts were perhaps not Miillerian ducts, 

 but enlarged segmental tubes with persisting abdominal funnels 

 belonging to the mesonephros. 



If the possibility of the oviduct of Lepidosteus not being 

 a Miillerian duct is admitted, a similar doubt must also exist as 

 to the genital ducts of other Ganoids, and we must be prepared 

 to shew that there is a reasonable ground for scepticism on this 

 point. We would in this connexion point out that the second 

 of the two arguments urged against the view that the genital 

 duct of Lepidosteus is not a Miillerian duct applies with equal 

 force to the case of all other Ganoids. 



The short funnel-shaped genital duct of the Chondrostei is 

 also very unlike undoubted Miillerian ducts, and could moreover 

 easily be conceived as originating by a fold of the peritoneum, 

 a slight extension of which would give rise to a genital duct like 

 that of Lepidosteus. 



The main difficulty of the view that the genital ducts of 

 Ganoids are not Miillerian ducts lies in the fact that they open 

 into the segmental duct. While it is easy to understand the 

 genesis of a duct from a folding of the peritoneum, and also easy 

 to understand how such a duct might lead to the exterior by 

 coalescing, for instance, with an abdominal pore, it is not easy 

 to see how such a duct could acquire a communication with the 

 segmental duct. 



We do not under these circumstances wish to speak dog- 

 matically, either in favour of or against the view that the genital 

 ducts of Ganoids are Miillerian ducts. Their ontogeny would 

 be conclusive on this matter, and we trust that some of the 

 anatomists who have the opportunity of studying the develop- 

 ment of the Sturgeon will soon let us know the facts of the case. 

 If there are persisting funnels of the mesonephric segmental 

 tubes in adult Sturgeons, some of them ought to be situated 

 within the genital ducts, if the latter are not Mullerian ducts ; 



1 F. M. Balfour, "On the Origin and History of the Urinogenital Organs of 

 Vertebrates," Journ. of Anat. and Phys., Vol. X., 1876 [This edition, No. VII]. 



