92 OTTO F. KAMPMEIER 
mouth of the former third intersegmental vein, and the extensions 
at the upper margin as the distal portion of this vessel. The 
anterior and posterior junctions of the lymph heart with the 
“ven-lym. com. jug. et 
¥:. «6S ? 
> oa 
nS ee: 
. proneph 
Fig. 17 Photomicrograph of a transverse section through the left anterior 
lymph heart region in a 6-mm. embryo of Bufo vulgaris (IX. E. C., series B 54, 
slide 2, section 130). X 340. si. proneph., the mouth of the original 3rd inter- 
segmental vein, branch of the pronephric sinus; proneph., pronephric tubule; 
med. spin., medulla spinalis. Other references as in figure 15. 
second and fourth intersegmentals, respectively, may also be 
resolved into plexiform channels. Thus, four fairly constant 
groups of connections may be recognized, a ventral, a dorsal, 
an anterior, and a posterior group. 
