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A. M. MILLER 



to the promontory there are also several vascular islands (5) 

 situated dorso-lateral to the postcardinal (2). These islands are 

 farther separated from one another than those along the line of 

 the precardinal. In this region also a few channels open into 

 the postcardinal. 



Fig. 1 Diagram drawn from a reconstruction of the A'eins in the cervical and 

 upper thoracic regions of a chick embryo of five days and twenty hours. Right 

 side. 1 , Precardinal vein ; 2, postcardinal vein ; 3, duct of Cuvier ; 4, intersegmental 

 (dorsal somatic) veins; 5, lateral group of venous islands (derivatives of and addi- 

 tions to which are represented by stippled areas in succeeding diagrams). 



There is a general tendency on the part of the intersegmental 

 veins (4) toward a division into medial and lateral branches. 

 The medial branches run close to the aorta and are obviously 

 the dorsal somatic veins proper, being in this region the cervical 

 intersegmental veins (fig. 2, 4). The lateral branches arise in 

 the same general region in which the above mentioned vascular 



