260 George 8S. Huntington and Charles F. W. McClure. 
secondarily the terminals of dorsal precardinal tributaries 1, 2 
and 3, which are taken up in the veno-lvmphatic organization. 
The two sides of this embryo present two distinct stages in the 
condensation of the peri-precardinal plexus and the subsequent 
separation of the resulting anlage of the cephalic division of 
the ventral plexus from the main channel. 
Reconstruction of Right Side, Lateral Aspect, Fig. 41. 
On the right side, the area receiving the terminals of dorsal 
tributaries 1, 2 and 3 in fig. 41, is plexiform and redundant. 
A portion of this plexus is condensed into a well-defined veno- 
lymphatic channel partially separated from the main vein by a 
fenestra through which the arrow passes in the figure. This 
channel, the principal anlage of the cephalic division of the 
ventral veno-lymphatic plexus, is a much more prominent struc- 
ture than its appearance would denote in the figure. 
It is also significant in this embryo that dorsal somatic tribu- 
taries 1, 2 and 3 are practically not involved in the development 
of the cephalic division of the ventral veno-lymphatic plexus, 
except in so far as their expanded terminals are included in the 
redundant precardinal area which is responsible for the formation 
of this portion of the plexus. 
The complex formed by the precardinal tributary 4 and its 
associated para-precardinal channel has separated into its dorsal 
somatic (4S) and veno-lymphatic (4VL) components. 
The dorsal somatic component of tributary 4 (4S, fig. 41) 
opens into the dorso-inedial circumference of the promontory and 
now forms the first of the promontorial series of somatic tribu- 
taries (4S, 5S and 6S, fig. 41). 
The veno-lymphatic derivative of the primary dorsal tributary 
4 (4VL, fig. 41) consists of an expanded, dilated and fenestrated 
sac which communicates with the precardinal at its primary point 
of connection with the latter (X in fig, 41; see also figs. 22 and 
23) and which also drains into the promontory through a para- 
precardinal channel that has developed from the peri-precardinal 
plexus in front of and contiguous to the promontory. Strictly 
