272 GEO. S. HUNTINGTON 



chymal cells which include all phases of developing blood cells, 

 differentiated in situ from the indifferent mesenchymal syncytium. 



2. These aggregations of developing blood cells are expecially 

 rich in erythrocytes. 



3. The blood cells are conveyed into the circulating stream of 

 the permanent blood vessels in one of two ways: 



a. Temporary haemal vascular channels form around the blood 

 islands, and after the latter' s resolution, carry the free blood 

 cells directly into an adjacent main venous trunk. 



This type is seen in mammalian embryos, especially in the 

 axial line, during the existence of the temporary ventro-medial 

 tributary plexus of the azygos veins, which plexus then atrophies 

 and is secondarily replaced by the independently developed peri- 

 venous anlages of the thoracic ducts. 



It is also encountered in the ventral mediastinal region where 

 an early perithymic plexus is replaced by the broncho-medias- 

 tinal lymphatic trunk, and in the development of the mesen- 

 teric lymphatic plexus. 



6. The early haemopoetic embryonal mesenchyme develops in 

 regions not directly associated with the permanent veins. The 

 blood cells are then conveyed to the general haemal circulation 

 by primitive lymphatic channels, which, after the performance 

 of this function, either remain as integral components incor- 

 porated in the lymphatic apparatus, or retrograde and ultimately 

 disappear. 



The early lymphatic system assumes therefor in these embryos 

 a special physiological duty, which we have defined as the haerno- 

 phoric function, in contrast to the haemopoetic character of the 

 early mesenchymal syncytial areas furnishing the free blood cells. 



A. M. Miller (26) has already defined this early haemophoric 

 function of the axial l3rmphatic trunks of the chick in the pre- 

 liminary note above quoted, and his extensive publication ap- 

 peared in the September issue of The American Journal of 

 Anatomy of last year (15). 



McClure, in a detailed study of lymphatic development in the 

 teleosts finds that in the trout lymphatic channels function more 

 extensively and for longer ontogenetic periods as blood-carriers 



