244 George 8. Huntington and Charles F. W. McClure. 
Tributary 1 (fig. 33, lateral aspect) enters the cephalic end of 
the straight precardinal segment by two branches, inclosing a 
wide fenestral space. The caudal of these two branches (fig. 33, 
1VL) opens into the dorso-lateral circumference of the precardinal, 
a circumstance which, in addition to its plexiform and dilated 
character, designates it as a veno-lymphatic structure. Here the 
crystallization of the plexiform reticulum into definite somatic 
and veno-lymphatie lines is still evident within the basal area of 
the tributary. 
Tributary 2 is represented by a veno-lymphatic component 
(2VL) which opens into the dorso-lateral, and by a dorsal somatic 
component (28, fig. 34), which opens into the dorso-medial cir- 
cumference of the precardinal. 
The original anastomosis between these components of 2 has 
in this instance been lost, and they now open into the precardinal 
as separate and independent tributaries. 
This interpretation is supported by the disposition of the suc- 
ceeding branches in this embryo. 
Dorsal somatic tributary 3 has separated into a lateral veno- 
lymphatic (3VL) and amedial dorsal somatic component (38). 
The veno-lymphatic component (3VL) consists of alargeexpanded 
double branch (3VL) and of asmaller caudal division (3VL’). Both 
of these veno-lymphatic elements open into the dorso-lateral 
circumference of the precardinal. 
The dorsal somatic component of tributary 3 (3S) is extremely 
small, and its relation to the veno-lymphatie element of this tribu- 
tary clearly indicates its original connection with the same. 
The veno-lymphatic components of the first three dorsal precardinal 
tributaries constitute the anlage of the Cephalic or Anterior Division 
of the Ventral Veno-Lymphatic Plexus. (Cf. figs. 10, 11, 12 and 13). 
The caudal or posterior division of the ventral veno-lymphatic 
plexus is already fully established. It is formed by the para- 
precardinal channel and by the veno-lymphatic components of 
4 (4VL in figs. 33 and 34); while the dorsal somatic element of 4 
(4S in figs. 33 and 34) now opens into the dorso-medial aspect of 
the promontory. 
The veno-lymphatic element of 4 represents the fenestrated 
