MULLERIAN AND WOLFFIAN DUCTS. 497 



The above series of sections goes far to prove that the 

 posterior part of the oviduct is developed as a nearly solid ridge 

 split off from the under side of the segmental duct, into which 

 at the utmost a very small portion of the lumen of the latter 

 is continued. One instance has however occurred amongst 

 my sections which probably indicates that the lumen of the 

 segmental duct may sometimes, in the course of the formation 

 of the oviduct and Wolffian duct, become divided into two parts, 

 of which that for the oviduct, though considerably smaller than 

 that for the Wolffian duct, is not so markedly so as in normal 

 cases (PI. 21, fig. 2). 



Professor Semper states that the lumen of the part of the 

 oviduct split off from the hindermost end of the segmental duct 

 becomes continuously smaller, till at last close to the cloaca it is 

 split off as a solid rod of cells without a lumen, and thus it comes 

 about that the oviduct, when formed, ends blindly, and does not 

 open into the cloaca till the period of sexual maturity. My own 

 sections do not include a series shewing the formation of a 

 terminal part of the oviduct, but Semper's statements accord 

 precisely with what might probably take place if my account of 

 the earlier stages in the development of the oviduct is correct. 

 The presence of a hymen in young female Elasmobranchs was 

 first made known by Putmann and Garman 1 , and subsequently 

 discovered independently by Semper 2 . 



The Wolffian duct appears to receive its first segmental tube 

 at its anterior extremity. 



In the male the changes of the original segmental duct have 

 a somewhat different character to those in the female, although 

 there is a fundamental agreement between the two sexes. As in 

 the female, a horizontal split makes its appearance a short way 

 behind the front end of the segmental duct, and divides this into 

 a dorsal Wolffian duct and a ventral Miillerian duct, the latter 

 continuous with the anterior section of the segmental duct, 

 which carries the abdominal opening. The differences in deve- 

 lopment between the two sexes are, in spite of a general similarity, 



1 "On the Male and Female Organs of Sharks and Skates, with special reference 

 to the use of the claspers," Proceed. American Association for Advancement of Science, 



1874- 



2 Loc . ci(. 



