LYMPHATICS IN FROG LARVAE 41 



It is a satisfaction, however, to insert the following quota- 

 tion from Kampmeier which, though differing in the concep- 

 tion of the primary plexus and its relations to the heart 

 (compare the accounts and figures of Kampmeier with those 

 of this paper), marks agreement with our original observa- 

 tions as to the part played by a primary plexus derived from 

 the veins in the origin of the anterior lymph hearts. 



On page 346 of Kampmeier 's paper of 1919 is this state- 

 ment: 



"The jugular lymphatic and the anterior lymph heart have 

 their origin in a venolymphatic plexus, derived from the first 

 three intersegmental veins which are an integral part of the 

 early vascular system of the embryo .... The anterior 

 lymph heart is produced from a close-meshed portion of the 

 plexus by the dilation and confluence of the channels and by 

 further distention of the single cavity so formed." 



(This is restated on p. 110 in the paper of 1922.) 



According to the interpretation offered for the reconstruc- 

 tions in toad embryos, the first three intersegmental veins and 

 their plexuses, together with the anterior lymph heart which 

 arises in these, become detached from their connections with 

 the pronephric sinus and other adjacent veins at a relatively 

 late stage to be transformed directly into the jugular lym- 

 phatics. (To follow these comments, refer to Kampmeier 's 

 paper of 1922 with the accompanying figures; see especially 

 fig. 33 of that paper.) 



The segmental veins are said to become suddenly converted 

 into a segmental chain of lymphatics immediately dorsal to 

 the lymph heart in 7-mm. toad embryos, and then to gradually 

 lose connections with the heart, leaving it completely isolated 

 in the 8-mm. toad an active larval stage (Kampmeier, '22, 

 fig. 34). The heart retains its attachment to the mouth of 

 the third vein, but is disconnected from the afferent lympha- 

 tics, with functions interrupted, according to this account, 

 and does not become finally incorporated in the lymphatic 

 system until the late 10-mm. larva (Kampmeier, '22, fig. 35). 



