Development of the Jugular Lymph Saes. 275 
the para-precardinal channel, is displaced ventro-caudad from the 
dorsal to the lateral surface of the precardinal and promontory, 
forming a dilated sac which communicates with the promontory 
at three points (area of Tap B, fig. 48), while in series 112 (fig. 47) 
the promontorial end of this correspondingly displaced portion 
of the ventral plexus consists of two parallel channels which open 
independently of each other into the lateral surface of the prom- 
ontory (Tap B, and B’, fig. 47). The difference in form, as well as 
the difference in the number of promontorial communications 
encountered in the two embryos, is due to varying phases of capil- 
lary condensation and amalgamation in the development of these 
partially detached portions of the ventral plexus. A comparison 
of figs. 44, 45, 47, and 48 clearly shows the transitional stages 
leading up to the conditions presented by series 113 (fig. 48). 
The second element (D) composing this anterior portion of the 
caudal division of the ventral plexus consists of a channel, lying 
cephalad of the promontory and parallel to the precardinal vein. 
It communicates with the latter at two points, and in addition, 
as above stated, is connected by a narrow curved channel with the 
first expanded sac-like element (V) on the lateral surface of the 
promontory. It, including its dorsal branches (4VL in fig. 48), has 
been derived from the original complex formed by precardinal 
tributary 4, and the para-precardinal channel. 
The original connection of element D with the promontory is, 
however, still represented by the most anterior of a series (1’, 2”, 
and E’’’) of small veno-lymphatic channels (fig. 48), which form 
together the posterior or caudal portion of the caudal division of 
the ventral plexus. This small veno-lymphatic (fig. 48, #”) opens 
into the promontory in line with the elements D of the anterior 
portion of the caudal division, and probably has become second- 
arily detached from the same in the course of development. Com- 
pare fig. 48 with fig. 33, in which a similar separation of the ventral 
plexus from the promontory at B has taken place, and with fig. 
42 in which the caudal division of the ventral plexus is alone 
represented by a small promontorial veno-lymphatic, the remain- 
der of the complex of tributary 4 having developed into dorsal 
somatic tributary 4S. 
