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proportions in which the two epithelia contribute in the formation 
of the wall. In an embryo of a length of 8.5 em the praeputium 
has grown round the whole glans. The orificium externum urethrae 
finds itself not far behind the apex of the penis on the perineal 
surface of the glans. 
The first sections, beginning at the apex of the penis, still show 
the solid phallus-frame (fig. 2 a). The aperture of the urogenital 
canal is to be seen in fig. 2 a as a groove in the thick mass of 
epithelium, having arisen by the meeting of the two edges of the 
praeputium. Through this the urogenital canal runs in an oblique 
direction and after some sections it reaches the surface of the glans. 
In that place the two lamellae of the phallus-frame have partly 
deviated a little from each other (fig. 2 b.). The adjoining penisecto- 
derm forms at the edges of the phallus-frame two small sexual folds 
(marked in fig. 2 b with g p). By the meeting of these two folds, 
some sections further on, the closure of the urogenital canal is brought 
about (fig. 2 ¢). In contradistinction to what we saw in the sphere 
of the fossa navicularis, the phallus-frame has by far the greatest 
part in the formation of the wall of che urethra; only a very small 
part proceeds from the sexual folds (penisectoderm). 
That here, also, the two wall-parts are easy to distinguish from 
each other, is taught by fig. 3, in which a part of fig. 2c under 
high power is sketched. 
The epithelium of the phallus-frame is to be recognized in a very 
distinct stratum germinativum of high cylindrical cells; between the 
stratum germinativum on either side there are a number of big, 
little coloured, polygonal cells with large round nuclei. The cell- 
boundaries are very clear. The groove between the deviated parts 
of the phallus-frame possesses a smooth surface. 
The epithelium proceeding from the penisectoderm and covering 
the foremost part of the canal, has quite a different appearance. 
It has a much darker colour, probably partially a consequence of 
the much closer arrangement of the nuclei. A clear stratum germi- 
nativum is not to be recognized, no more are the cell-boundaries 
visible; the limitation of the lumen is not so smooth and sharp as 
in the phallus-frame. 
If we follow the urethra towards the fossa navicularis, we see 
two kinds of changes taking place. First in the wall-formation a place 
getting larger and larger is given to the penisectoderm; secondly the 
two lamellae of the phallus-frame deviate more and more, only a 
small part remaining in the shape of a crest on the urethra (fig. 2e). 
The epithelium of the phallus-frame is gradually replaced by an 
