DEVELOPMENT OF LYMPHATICS IN ANURA 105 
diagrammatic. It develops, however, at the same time as the 
other valve. In 7-mm. embryos the lymph heart is still in broad 
open communication with the anlage of the vertebral vein (fig. 18). 
In the next few succeeding stages (8-, 9-, and 10-mm. embryos) 
the junction becomes progressively constricted by the local 
thickening of its surrounding wall. In fact, in some cases it 
was observed that the cell proliferation was so considerable as to 
block almost entirely the channel of connection (figs. 19 and 22). 
cor lym. ant. 
Si. SUDSCAD. 
Fig. 24 Quasischematic reconstruction of the left anterior lymph heart of 
the young toad immediately after metamorphosis. 150. Ventromedial 
view. cor lym. ant., cor lymphaticum anterius; v. vert. ant., vena vertebralis 
anterior; si. subscap., subscapular sinus; af., one of the afferent portals. 
Then, by the elongation of its thickened sides (fig. 25,*) asso- 
ciated with the expansion of the venous lumen up and around it 
towards the lymph-heart wall, the connection becomes telescoped, 
as it were, into the cavity of the vein, so that the thickened cell 
masses project as the lips of the valve (fig. 26,*). This process 
is completed in 10- to 12-mm. toad embryos (B. vulgaris). In 
the outline sketches in figure 27, the formation of both the afferent 
and the efferent portal is expressed graphically. 
