176 OTTO FREDERIC KAMPMEIER 



rudiments in the trunk region. It is clear also that were the 

 cephalic mesenchyme more amply furnished with yolk from the 

 start and would lose it more tardily, the discovery of the funda- 

 mental moment in lymphatic development in toad embryos 

 would have been by far more difficult and tedious and the evidence 

 less striking. Yet the judicious reader cannot contend for the 

 direct mesenchymal origin of the lateral lymph ducts of the 

 trunk after he has carefully inspected the figures illustrating their 

 anlagen; nor can he, though this remark be irrelevant at this 

 point, conscientiously claim for them continuity in development. 

 The genesis of the inferior lateral lymph duct accompanying 

 the postcardinal vein (cf. fig. 15) evinces the actuality of dis- 

 continuity in a large developing lymphatic vessel probably more 

 forcibly than does the genesis of the two vessels already considered. 

 Figure 27 was drawn from a section of a 6 mm. embryo through 

 the posterior portion of the anterior lymph heart. From the 

 ventro-lateral aspect of the heart (l.h.) a vessel (L), the foremost 

 anlage of the lymph duct, is given off which at first turns down- 

 ward between pronephric duct (w.) and epidermis (ep.) and then 

 backward. After continuing in this direction for eight sections, 

 it ends blindly, the termination being shown in figure 28 (Z.). 

 Between this and the anterior limit of the next succeeding anlage 

 there is an interval of twenty-five sections in which lymphatic 

 rudiments or anything resembling them are absent, at least are 

 not in evidence. The territory between pronephric duct, lateral 

 postcardinal division and epidermis is in possession of apparently 

 only mesenchymal cells as pictured in the sketched section, 

 figure 29, which typifies the character of this region. After such 

 an interval the blunt tip of a discrete endothelial-lined space 

 suddenly springs into view (Z., fig. 30). The next section (fig. 31) 

 reveals plainly other salient features of this rudiment (/.). It 

 composes a well-defined and closed cavity, the confines of which 

 are strong and firm, and like those of the vein (p.l.) contain many 

 yolk globules; in brief, there is no feature, except perhaps its 

 large rotund nuclei, which could cause it to be confused with the 

 mesenchyme. But the nuclei do not offer a serious hazard in 

 the matter, for we have seen that the nuclei of the initial lymph 



