444 F. M. Balfour and A. Sedgwick on the Existence [May 23, 



The first trace* of the Miillerian duct we have met with is a very- 

 shallow groove in the germinal epithelium some little way behind 

 the front end of the Wolffian body, and nearly overlying, though 

 slightly external to, the Wolffian duct. 1 This stage corresponds with 

 the earliest stage described by Dr. Grasser.f In the next stage, 

 which follows very closely upon the first one, remarkable changes 

 have taken place in the groove, which can best be explained by 

 describing the appearance of a series of successive sections from 

 before backwards through the groove and its continuation. 



Anteriorly there appears in section a simple groove, which, after a 

 short distance, is suddenly replaced by an apparently solid thickening 

 of the germinal epithelium. An open groove again appears in this, 

 which in its turn is succeeded by a thickening, which is next converted 

 into a definite ridge, projecting inwards towards the Wolffian duct, 

 in which, we believe, we have observed a rudimentary lumen. After 

 one or two sections, a slit-like opening appears, placing the lumen 

 in the ridge in communication with the body cavity, and, in fact, a 

 groove somewhat deeper but otherwise exactly similar to that visible 

 in the anterior sections has reappeared. This groove after being con- 

 tinued for two or three sections again becomes closed, and its walls 

 are prolonged as a nearly solid rod which cannot be traced beyond one 

 or two sections. In general terms, the change which has taken place 

 is, that the opening of the primitive simple groove has been divided 

 into three, and the three separate grooves are connected by a rod-like 

 structure developed from part of the wall of the original groove, in 

 which a lumen either exists from the first, or very soon appears. 



In the next stage, the anterior part of the Miillerian duct is formed 

 of a tube communicating by, at the least, three separate apertures 

 with the body cavity, and the tube connecting these is perhaps slightly 

 convoluted. The hindermost opening of the duct is continuous with 

 a rod-like body which may be traced backwards for some little dis- 

 tance. It is hollow in front, and terminates by a solid point, in a 

 manner which we propose describing in detail in a fuller paper, with 

 illustrations. 



This peculiar condition of the abdominal opening of the Miillerian 

 duct does not last for long, and before the Miillerian duct has nearly 

 grown back to the cloaca, it opens in front by a single elongated 

 groove. At this period, its hind end, or growing point, instead of 

 being conical, is rounded, and the lumen of the duct is continued into 

 the rounded extremity. 



So far as we know, none of the very divergent accounts which have 



* We do not give the number of hours of incubation, as we find these are too 

 inconstant to be of any scientific value. 



f " Entwicklungsgeschichte d. Allantois d. Muller'schen Gange u. d. Afters." 

 Frankfurt, 1874. 



