196 George 5. Huntington and Charles F. W. MeClure. 
Association of American Anatomists in 1906" and is well illus- 
trated by figs. 4, 5, 6, and 7 which are photomicrographs of 
transverse sections of a 16 mm. cat embryo taken at the level at 
which the external jugular joins the jugulo-cephalic trunk. Figs. 
4, 5, 6 and 7 represent, respectively, sections 233, 237, 239 and 
241 of series 15. 
DEVELOPMENT OF THE VENO-LYMPHATIC PLEXUSES AND SACS OF 
THE EARLY EMBRYONIC STAGES AND THE ESTABLISHMENT 
OF THE STRUCTURAL BASIS FOR THE SUBSEQUENT DEVELOP- 
MENT OF THE JUGULAR LYMPH SACS. 
The general development of the jugular lymph sacs in the eat 
presents four successive periods: 
1. THE PRIMARY VENOUS STAGE, in which the ground-plan of 
the primitive embryonic venous system is laid down. 
These early embryonic venous channels appear to crystallize 
out of an antecedent capillary network along definite hydrostatic 
lines. 
2. VENO-LYMPHATIC STAGE, In which, with reduction and further 
definition of the venous channels, a portion of the same is sur- 
rounded in certain areas by a secondary capillary network which, 
together with a larger or smaller portion of the main embryonic 
vein, is condensed into a uniform structure and separates from the 
permanent venous channel as the anlage of the future jugular 
lymph sae. 
In view of the double relation which this structure sustains, on 
the one hand to the embryonic venous system from which it is 
directly derived, and on the other to the general lymphatic 
system with which it establishes secondary connections, we have 
designated this period as the Veno-Lymphatic Stage in the develop- 
ment of the definite jugular lymph sac, and have described the 
portions separated from the early venous channels as the Veno- 
Lymphatic Plexuses or Sinuses, which form the anlage of the 
final definite jugular lymph sac. 
3. PRE-LYMPHATIC STAGE, in which the early veno-lymphatic 
plexus becomes sac-like and evacuates its blood-contents, and 
' f’untington and McClure. Figs. 14 to 17 inclusive, in vol. 2 of The Anatomi- 
cal Record. 
