182 OTTO FREDERIC KAMPMEIER 



which correspond, as the writer will show in the later paper, to 

 the two anterior centers, the jugular lymph sacs, in Alammalia. 



Finally, a certain peculiarity in the development of lymphatic 

 channels in Bufo has suggested a possible homology between the 

 incipient anlagen here observed and peri-venous lymphatic 

 spaces first discovered and described by Huntington and McClure 

 in cat embryos. ^1 Opponents of this view of lymphatic formation 

 maintain that such spaces are artificial, due to shrinkage, though 

 adequate proof to uphold this contention is not forthcoming. 

 As has been shown in the figures, there occur in certain stages of 

 the toad lar\'ae hollow lymphatic anlagen which hug the vein 

 closely and consequently resemble extra-intimal spaces, but which 

 have been shown to be really intra-intimal in nature since their 

 lumen arises as a vacuolation of the endothelial proliferation. 

 Might not a similar condition be found to prevail in mammalian 

 embryos were the genesis of extra-intimal spaces followed back 

 far enough? 



In the writer's judgment, it is only by carrying out extensive 

 and minute cytological studies in all classes of vertebrate embryos, 

 to determine specific cell character and behavior of both mesen- 

 chyme and endothelium during the very early genetic stages, 

 that we can arrive most surely and quickly at a uniform and com- 

 prehensive conception of lymphatic development and can mea- 

 sure the amount of truth and the number of fallacies inherent 

 in the several respecti\'e theories hitherto advanced. This may 

 prove to be an arduous task inasmuch as a natural and peculiar 

 diagnostic trait, like that of yolk content, to distinguish incipient 

 lymphatic intima from mesenchyme, probably does not exist in 

 embryos other than Amphibian, but by the invention and appli- 

 cation of different staining methods the results would perhaps 

 be quite as surprising. 



'1 Huntington and McClure; Am. Jour. Anat., vol. 6, 1907, Anat. Rec, no. 3. 



