MULLERIAN DUCT IN BIRDS. 499 



me erroneously, the existence of the posterior rudimentary parts 

 of the Mullerian duct. He further asserts that the portions of 

 the Mullerian duct with a lumen open into the Wolffian duct. 

 The most important difference, however, between Professor 

 Semper's and my own description consists in his having failed to 

 note that the splitting of the segmental duct commences much 

 further forwards in the male than in the female. 



I have attempted to shew that the oviduct in the female, 

 with the exception of the front extremity, is formed as a nearly 

 solid cord split off from the ventral surface of the segmental 

 duct, and not by a simple splitting of the segmental duct into 

 two equal parts. If I am right on this point, it appears to me 

 far easier to understand the relationship between the oviduct 

 or Mullerian duct of Elasmobranchs and the Mullerian duct of 

 Birds, than if Professor Semper's account of the development of 

 the oviduct is the correct one. Both Professor Semper and my- 

 self have stated our belief in the homology of the ducts in the 

 two cases, but we have treated their relationship in a very 

 different way. Professor Semper 1 finds himself compelled to 

 reject, on theoretical grounds, the testimony of recent observers 

 on the development of the Mullerian duct in Birds, and to assert 

 that it is formed out of the Wolffian duct, or, according to my 

 nomenclature, '.the segmental duct.' In my account 2 , the ordinary 

 statements with reference to the development of the Mullerian 

 duct in Birds are accepted ; but it is suggested that the indepen- 

 dent development of the Mullerian duct may be explained 

 by the function of this duct in the adult having, as it were, more 

 and more impressed itself upon the embryonic development, 

 till finally all connection, even during embryonic life, between 

 the oviduct and the segmental duct (Wolffian duct) became lost. 



Since finding what a small portion of the segmental duct 

 became converted into the Mullerian duct in Elasmobranchs, I 

 have reexamined the development of the Mullerian duct in the 

 Fowl, in the hope of finding that its posterior part might develope 

 nearly in the same manner as in Elasmobranchs, at the expense 

 of a thickening of cells on the outer surface of the Wolffian duct. 



1 Loc. cit. pp. 412, 413. 



2 " The Urinogenital Organs of Vertebrates," Journal of Anatomy and Physiology, 

 Vol. x. p. 47. [This edition, p. 164.] 



