DEVELOPMENT OF THE JUGULAR LYMPH SAC 



477 



Fig. 2 From a photograph of a section through the cervical region of a chick 

 embryo of five days and twenty hours (embryo from which the reconstruction 

 represented in fig. 1 was made). 1, Precardinal vein; 4, intersegmental cervical 

 (dorsal somatic) veins; 5, lateral group of venous islands (represented in fig. 1 

 by stippled areas); 6, aorta; 7, cesophagus; 8, notochord. 



islands (5) are situated. Despite the fact that at this stage 

 there is a tendency toward a separation of the vascular channels 

 and islands into a medial group and a lateral group, they appar- 

 ently all belong in the same category, namely, an aggregation of 



