264 George 8. Huntington and Charles F. W. McClure. 
This embryo shows most clearly that the veno-lymphatic area 
of the promontory has differentiated along its dorso-lateral cir- 
cumference, leaving its dorso-medial aspect free for the entrance of 
the dorsal somatic tributaries (4S, 5S, 6S and 7S, fig. 42). A 
similar dorso-lateral position with respect to the precardinal has 
already been described and emphasized as being characteristic of 
the veno-lymphatic derivatives of its dorsal tributaries (see figs. 
33, 34, etc.). 
In general, the relative position of the dorso-lateral veno-lymphatie 
(dorsal veno-lymphatie plexus and caudal division of ventral veno- 
lymphatic plexus) and the dorso-medial somatic (48, 5S, 6S) ele- 
ments with respect to each other and to the precardinal vein, is 
clearly shown in fig. 43, which is a photomicrograph of a transverse 
section of al0 mm. cat embryo taken at a level just anterior to 
the jugular promontory (series 114, slide 4, section 27). 
Series 102, 8.5" Embryo 
Reconstruction of the left side 
Lateral aspect, fig. 44 and 
Medial aspect, fig. 45 
Reconstruction of right side, 
Lateral aspect, fig. 46 
Although this embryo measures less than other members of 
this group, due probably to a greater degree of body and head 
curvature, it represents a more advanced stage of development, 
which bridges the interval between the intermediate and defi- 
nitely established veno-lymphatic periods. 
Reconstruction of Left Side, Lateral Aspect, Fig. 44. 
The three primary divisions of the veno-lymphatic plexus are 
fully established. 
With the exception of the element contributed by dorsal tribu- 
tary 1 (1VL), which forms a dilated and fenestrated sac, connected 
with the precardinal, all of the components of the ventral division 
of the veno-lymphatic plexus have fused with one another to 
form a large and multi-fenestrated sac. 
EE —— 
