292 George 8. Huntington and Charles F. W. McClure. 
and fenestrated appendage (fig. 50, b) which is also seen in series 
77 (fig. 51,b). From the position of this element b,it seems prob- 
able that its junction with the small anterior tap of evacuation 
will establish the wide portal of entry, which in series 78 (fig 57) 
forms the main anterior connection of the sac with the veins. In 
this case it appears likely that the small caudal connection in ser- 
ies 78 (fig. 57) represents the original anterior tap as seen on the 
right side of series 101 (fig. 50), and on both sides of series 77 (figs. 
50, 51, and 52). Finally, on the left side of series 101 (fig. 49), a 
stage is shown, just prior to the establishment of the anterior tap 
of evacuation, in which the dorsal veno-lymphatic arch has not 
yet: united with the anterior precardinal veno-lymphatic elements 
to form the anterior tap of evacuation. 
4. The blood contents of the earlier veno-lymphatic plexus 
have for the most part, been completely evacuated on the left 
side of this 12 mm. embryo (fig. 57), evidently through the large 
anterior venous connection just described. Here and there in the 
caudal portion of the sae small outlying pockets still contain a 
few blood cells, but as a whole the former veno-lymphatic plexus 
represents on this side an enormously expanded empty sac, de- 
detached at all points from the venous system except at the very 
large and the small anterior channels described. A comparison of 
the left (fig. 57) with the right side of this embryo (not figured) is 
most instructive. On the right side the sac is completely closed, con- 
tains no blood corpuscles and, as far as we can determine, does not 
communicate with the veins at a single point. Since the promontor- 
ial connections of the sac in both of the embryos which immediate- 
ly precede this stage appear to be too insignificant to permit of 
the passage of a large amount of blood, we can only infer that on 
the right side, as on the left, an anterior tap of evacuation was at 
one time present, and that it served as the main exit for the blood 
contents of the veno-lymphatic sac. Figs. 53 and 54 (series 78, 
slide 3, sections 34 and 40) show the appearance of the anterior tap 
of evacuation and of the connected portion of the sac in transverse 
section on the left side, and, on the right side, the complete sep- 
aration of the jugular sac from the veins. Figs. 55 and 56 show the 
caudal portion of the lymph sac (slide 4, sections 33 and 35). 
