286 GEO. S. HUNTINGTON 



inexcusable to Fletcherize an idea to this extent, but I feel com- 

 pelled to again point out that the difference between the ce7i- 

 trifugal and the centripetal theory of development of the verte- 

 brate lymphatics is not merely one of direction. The former 

 involves the concept of a continuous uninterrupted centrifugal 

 extension of Ijmiphatic growth from one or more central foci, 

 in this case the endothelium of certain venous channels. The 

 centripetal theory is based on the development of the finally 

 continuous lymphatic channels by the union of separate and 

 independently developed lymphatic anlages into a connected 

 vascular system, in exactly the same way as the earliest anlages 

 of the blood vessels unite into a continuous whole. Observation 

 shows that the direction of this union in case of the lymphatic 

 system is from the periphery toward the center, but this ele- 

 ment is of less morphological importance than the actual process 

 of lymphatic vasculo-genesis. 



Apparently Fedorowicz has never considered the possibility 

 that between his extracardial lymphatic anlages and the longi- 

 tudinal lymphatic trunks of the tail there may exist a series of 

 independent intercellular lymphatic mesenchymal spaces whose 

 union with each other and with the central and peripheral links 

 of the chain will merely repeat the process of secondary junction 

 which he has so carefully described between the earliest lym- 

 phatic extracardial anlages and the cavity of the l>^nph heart. 

 At any rate, failing the proof that such intermediq,te connecting 

 anlages do not develop, and in view of the fact that the only 

 phase which Fedorowicz has observed and described is the cen- 

 tripetal union of independently developed extracardial lymphatics 

 with the hearts, it is difficult to see the validity of his conclusions: 



Ueberdies miissten sie (the extracardial lymphatics) entweder schon 

 vorhanden sein ehe die Herzen angelegt wiirden (why?) oder sie wiirden 

 an den Herzen erst sichtbar sein wenn sie an dieselben von der Peri- 

 pherie herangewachsen waren. (why?) .... Somit sind die an 

 den Lymphherzen sich bildenden Zellstrange als Anlagen der Lymph-' 

 gefasse anzusehen, die von den Herzen nach der Peripherie auswachsen. 



If these conclusions were true, why do the earliest extra- 

 cardial lymphatics at first extend from the extracardial area 



