518 MR GREGG WILSON ON THE DEVELOPMENT 



in which " der solide Strang, welcher die Anlage des Miiller'schen Ganges darstellt, 

 direct dem erhohten Peritonealepithel anlagert, olme aber seine Selbstandigkeit ihm 

 geojeniiber aufzugeben." 



The argument seems unsound, inasmuch as it implies that if a duct is derived from 

 the epithelium, it must continue at least for a considerable time to show its connection 

 with it. In the later stage made use of by Furbringer to settle the point, the develop- 

 ment was so far advanced that the Mullerian duct was provided with a fine lumen. 

 I conceive, therefore, that the cord of cells may have been of epithelial origin, as 

 Furbringer himself thought from his examination of stage " C." The facts do not 

 satisfactorily prove, as Furbringer maintains, that the origin of the Mullerian duct is 

 independent of the peritonealepithelium : growth backwards from an anterior epithelial 

 thickening is certainly not excluded. 



Hoffmann's description of the processes that precede the formation of the Mullerian 

 duct in Rana and Triton also correspond largely with what I have observed. As to 

 Rana he writes : " Der Muller'sche Gang ist jetzt noch nicht " (at the time of separation 

 of segmental duct and pronephros) " zur Anlage gekommen, bevor dies stattfindet, 

 zeigt das Peritonealepithel, welches den noch bestehenden Theil des Pronephros beklei- 

 det, eigenthiimliche Veranderungen, indem es sich in ein holies schmales Cylinderepithe- 

 lium umbildet ; diese Umwandlung der platten Peritonealzellen in hohe Cylinderzellen 

 dehnt sich lateralwarts noch eine bedeutende Strecke weiter aus als der Pronephros 

 reicht und setzt sich selbst ventral warts noch fort." And after describing the 

 separation of segmental duct and pronephros, he goes on to narrate that the blind 

 anterior end of the former " legt sich nun dem erhohten Peritonealepithel des fortwiihr- 

 end mehr und mehr sich zuriickbildenden Pronephros an und verlothet sich mit ihm." 



It is subsequent to this, according to Hoffmann, that the Mullerian duct is origin- 

 ated by a splitting of the segmental duct — or rather of a small part of it. 



In like manner a cylinder epithelium " neben und zwischen den beiden Trichtern" 

 is described as occurring in Triton, "bevor der Muller'sche Gang sich angelegt hat " ; 

 and a splitting of the segmental duct is said to occur at the anterior end. 



The division of the segmental duct in Rana is not figured, but it is not difficult to 

 see that a mistake might very readily arise by some " small part " of the Anlage of the 

 Mullerian duct being applied more closely than usual to the degenerating segmental 

 duct. 



The splitting in Triton is illustrated, but not so as to carry conviction ; the figures 

 numbered " 15," " 16," and " 17 " might very well represent a simple change of position 

 of the duct " W.g." from a more dorsal to a more ventral position, and the other series 

 " 18 " to " 20 " might likewise illustrate a change in the opposite direction. Time after 

 time I have found similar series in the anterior region of the segmental duct, for where 

 a change of position occurs the duct not uncommonly doubles back on itself (cj. figs. 3 

 and 4, and 8 to 11). 



I suggest, then, a possible explanation of the published figures. I venture to do 



