Charles F. W. McClure 207 
The writer has already described in a previous paper (McClure, 00, 
2, p. 457) the variable manner in which the Vy. pudendovesicales of 
the adult may open into the iliac veins. They may open in the adult into 
the angle of union of two veins which join the external and internal iliac 
veins, respectively, ventral to the iliac arteries; or, they may open into 
the angle of union of three veins, two of which lie ventral to the arteries 
and join the iliac veins as above, while the third les dorsal to the arteries 
and joins the external iliac vein (see McClure, 00, 2, Figs. 20 and 21). 
Also, they may open as single vessels on each side either into the external 
or internal iliac veins (Fig. 16, Plate IV, Part 1); or, into the external 
iliac vein on one side and into the internal iliac on the other (Fig. 9, 
Pilate: id, ‘Part.1). 
Cases in the adult in which the V. pudendovesicalis opens into the 
angle of union of two veins which join the external and internal iliacs, 
respectively, ventral to the arteries (as in Fig. 4, right side, Plate I, 
Part I, and in Fig. 10, right side, Plate II, Part I) can be explained on 
the ground of the persistence of the ventral portion of the lateral cir- 
cumarterial venous ring. Cases in the adult in which the V. pudendo- 
vesicalis opens as a single vessel into either the external or internal iliac 
vein (Figs. 8 and 9, Plate II, Part I) can also be explained on the ground 
that the ventral portion of the lateral venous ring gives up its connection 
with one or the other of the iliac veins so that the V. pudendovesicalis 
will necessarily open only into the iliac vein with which the connection 
has been retained. 
Although those cases in which the V. pudendovesicalis opens into the 
external and internal iliac veins, ventral to the arteries, appear to find 
an explanation, it is not so clear how this vein, as is frequently the case 
in the adult, makes connections with the iliae veins dorsal to the iliac 
arteries. It is possible that a considerable number of reconstructions of 
the pouch young would show that the V. pudendovesicalis does not al- 
ways open into the iliac veins as represented in Text Fig. 17, but that it 
may also, in some instances, open into the angle of union of two veins 
which, as in the case of an adult, join the external iliac vein dorsal and 
ventral, respectively, to the external iliac artery (see Fig. 4, left side, 
Plate I, Part I). It is evident, if this case of the adult represents the 
persistence of a condition which sometimes prevails in the pouch young 
we then have an explanation of those peculiar cases in which the V. pu- 
dendovesicalis opens into the iliac veins dorsal to the iliac arteries. 
Finally, I think it may be stated without fear of refutation, that the 
variable character of the V. pudendovesicalis in the adult is correlated 
with the variable manner in which the iliac veins unite to form the post- 
