THE URINOGENITAL ORGANS OF VERTEBRATES. 149 



common opening. For further details vide Hyrtl, Denk. der k. 

 Akad. Wien, Vol. n. 



It is possible that the generative ducts of Osseous fishes are 

 derived from a splitting from the primitive duct of the kidney, 

 but this is discussed later in the paper. 



In Osseous fishes we probably have an embryonic condition 

 of the Selachian kidneys retained permanently through life. 



In the majority of Ganoids the division of the segmental 

 duct of the kidney into two would seem to occur, and the ventral 

 duct of the two (Miillerian duct), which opens at its upper end 

 into the body-cavity, is said to serve as an excretory duct for 

 both male and female organs. 



The following are the more important facts which are known 

 about the generative and urinary ducts of Ganoids. 



In Spatularia (vide Hyrtl, Geschlechts u. Harnwerkzeuge bei 

 den Ganoiden, Denkschriften dcr k. Akad. Wicn, Vol. viil.) the 

 following parts are found in the female. 



(1) The ovaries stretching along the whole length of the 

 abdominal cavity. 



(2) The kidneys, which are separate and also extend along 

 the greater part of the abdominal cavity. 



(3) The ureters lying on the outer borders of the kidneys. 

 Each ureter dilates at its lower end into an elongated wide 

 tube, which continues to receive the ducts from the kidneys. 

 The two ureters unite before terminating and open behind 

 the anus. 



(4) The two oviducts (Miillerian ducts). These open widely 

 into the abdominal cavity, at about two-thirds of the distance 

 from the anterior extremity of the body-cavity. Each opens by 

 a narrow pore into the dilated ureter of its side. 



In the male the same parts are found as in the female, but 

 Hyrtl found that the Miillerian duct of the left side at its 

 entrance into the ureter became split into two horns, one of 

 which ended blindly. On the right side the opening of the 

 Mullerian duct was normal. 



In the Sturgeon (vide J. Miiller, Ban u. Grcnzen d. Ganoiden, 

 Berlin Akad. 1844; Leydig, FiscJien n. Reptilicn, and Hyrtl, 

 Ganoiden} the same parts are found as in Spatularia. 



