254 George F. Huntington and Charles F. W. McClure. 
present instance, having lost its connection with the precardinal 
tributary 4, it functions in a manner similar to that of the more 
ventrally situated main precardinal channel and_ represents 
an advanced stage in the separation from the latter of what con- 
stitutes the anlage of the caudal division of the ventral veno- 
lymphatic plexus. 
The veno-lymphatic development along the dorso-lateral cir- 
cumference of the promontory and posteardinal vein has pro- 
gressed to a slightly greater extent than on the right side. The 
broken line along the promontory (fig. 39) shows the extent to 
which the veno-lymphatiec ridge projects from the promontory. 
The anterior end of the dorsal veno-lymphatic plexus extends for- 
ward over the para-precardinal ¢ghannel, where it ends blindly and is 
continuous caudad with the anlage common to the primitive 
ulnar vein and primitive ulnar veno-lymphatic. This vessel opens 
into the posteardinal by means of a single channel, and caudad of 
this point, as on the right side, it has completely separated from 
the postcardinal. 
We have here an instance, as on the right side of this embryo, 
in which the first promontorial dorsal somatic tributary (5 S, fig. 
39) vs represented by the fifth of the series, and in which, in all proba- 
bility, precardinal tributary 4 has been transformed in its entirety 
into veno-lymphatic components which will aid in the forward exten- 
sion of the dorsal veno-lymphatic plexus. Also, on the left side, 
fig. 89, a case in which the caudal division of the ventral veno-lym- 
phatic plexus is derived solely from the para-precardinal channel. 
Compare figs. 39 and 40. 
SUBSEQUENT EARLY STAGES ILLUSTRATING VENO-LYMPHATIC 
DEVELOPMENT 
Series 102, 8.5" Embryo 
Series 106, 9°" Embryo 
Series 19, 9°" Embryo 
This group of embryos presents the following features of veno- 
lymphatic development in advance of those described in connec- 
tion with the preceding group: 
