DEVELOPMENT OF LYMPHATICS IN ANURA 103 
(fig. 26). It is possible that these trabeculae correspond to the 
incomplete partition which, according to Radwanska (’06), is of 
constant occurrence in the anterior lymph hearts of adult frogs. 
b. The afferent portals. As was indicated earlier, during the 
first part of its functional life the lymph heart of the anuran 
embryo possesses but two valvular openings, a lymphaticovenous 
or efferent one and the entrance of the afferent lymph vessel. 
It is only in later embryonic and postmetamorphic periods that 
the number of afferent gateways is increased from one to about 
twelve. The development of this type will be considered first. 
In the discussion of the morphogenesis of the lymph heart the 
writer has described how the developing lymphatic plexus sur- 
rounding it temporarily detaches and recedes from it and how 
the longitudinal channel of the plexus, the common segment of 
the jugular and lateral-line ducts lying dorsal to the heart, again 
comes into juxtaposition with it by the dilatation of both struc- 
tures, whereupon the permanent communication is established. 
Figure 20 is a section of the lymph-heart region during the phase 
of simple apposition. Here the heart wall, having the same 
appearance and thickness as elsewhere along its periphery, sepa- 
rates the cavity of the heart (cor. lym. ant. sin.) from that of the 
lymph duct (lym. com. jug. et lat.), and there is as yet no indica- 
tion of the future opening between the two. In the next older 
stage (10-mm.), the heart and vessel are more intimately applied 
to each other by the partial invagination of the latter into the 
heart, as shown in figure 21 (*); in the reconstruction (fig. 35) the 
vessel lies in a shallow furrow of its heart wall at af. It is along 
this surface of contact that the partition dividing the two cavities 
thickens considerably (fig. 21) by the proliferation of its cells: 
Somewhat later, a cleft develops in the center of the thickened 
area (fig. 22, *) by the separation of its cells, evidently the effect 
of the increasing pressure within the afferent lymph duct. The 
margins of the simple rupture now serve as the valve. These, 
by further proliferation, may become longer, and as they converge 
and project into the lumen of the lymph heart they produce the 
typical teat-like form in section (fig. 23, *). The other valvular 
afferent portals which arise later (fig. 24, af.) are developed in 
