40 HENRY MCELDERRY KNOWER 



The results for the toad are claimed to be typical for other 

 Anura as well, but examination of the early lymphatics pic- 

 tured in the reconstructions of toad larvae compared with the 

 system shown in injections of frog embryos reveals serious 

 disagreement between the two. The following analysis of 

 these differences is, therefore, undertaken in the hope of 

 making clear what may be reasonably accepted. 



DISCUSSION OF DIFFERENCES BETWEEN RECONSTRUC- 

 TIONS OF EARLY LYMPHATICS OF THE TOAD 

 AND INJECTIONS OF THESE VESSELS 

 IN FROG LARVAE 



The reconstruction method has been applied with such 

 thoroughness by Kampmeier that the models presented are 

 evidently exceptionally good examples of its use. 



Criticisms of the reconstructed lymphatics of toad embryos 

 should then be understood as chiefly directed against the 

 limitations of the method in dealing with material like that 

 of young Amphibia, in which the early lymphatics are not 

 readily distinguished from veins or tissue spaces in sections 

 of uninjected specimens. 



In the toad, the lymphatic system is represented as assem- 

 bled or growing together from three widely separated centers, 

 with a different method of origin for each center. 



The first lymphatics are said to arise in this form as a de- 

 tached group in the submaxillary region, either from the walls 

 of veins or from isolated tissue spaces nearby, the group not 

 joining the central vessels associated with the anterior lymph 

 heart until relatively late. In comparing injections with the 

 reconstructed models of the toad lymphatics, the original 

 papers (Kampmeier, '15- '25) describing the latter should be 

 freely consulted, since his data cannot be reproduced here. 

 Such detached origin of peripheral groups of lymphatics is 

 not found in injections. 



The anterior lymph hearts with their associated plexuses, 

 described in earlier accounts by Hoyer and Knower as the 

 first lymphatics to arise in both toads and frogs, are rele- 

 gated by Kampmeier to second place in order of appearance 

 in toad embryos. 



