282 GEO. S. HUNTINGTON 



from preexisting endothelium, it has no connection with any- 

 haemal endothelimn, venous, arterial or capillary, and it never 

 had such a connection. Let us hope that observations, such as 

 Allen's, if sufficiently and laboriously multiplied, may finally 

 eradicate from 'modern' anatomical and embryological textbooks, 

 such as the recent Keibel-Mall publication, that unfortunate 

 dogma charged to Rabl, ''Alles Endothel stammt von Endothel!" 



Allen's work further touches on one phase of the early intra- 

 embryonic haemopoesis. He finds that, within the early lym- 

 phatic anlages, "certain of the enclosed cells increase in size, 

 become spherical and differentiate into red* corpuscles." Speak- 

 ing of the lymphatic or veno-lymphatic organization of Polisto- 

 trema he states that '*in all of the larger or medium-sized em- 

 bryos the connective tissue outside these (lymphatic) vessels 

 was so filled with red corpuscles as to resemble germination 

 centres, and the vessels themselves appeared to be reservoirs for 

 storing them." 



Allen, on page 350 of his paper, sums up the development of 

 the caudal hearts in Polistotrema as ''a vacuolation of the mesen- 

 chyme by the disintegration of certain of the mesenchyanal cell 

 processes, and the flattening of some mesenchymal cells to become 

 endothelium, and a rounding of others to become red corpuscles." 

 This description is in complete agreement, in every important 

 morphological aspect, with Miller's discovery of the development 

 of the avian axial lymphatics (15, 27). 



Stromsten, in two publications (25, 26) describes the develop- 

 ment of the posterior lymph hearts in turtles (loggerhead turtle, 

 Thalossochelys caretta). He states (26, p. 175) that: 



The development of the posterior lymph hearts is initiated in the 

 loggerhead turtle by the vacuolation of the subcutaneous mesenchymal 

 tissue of the post-iliac regions. As early as the middle of the second 

 week .... the mesenchyme becomes very loose and spongy-. 

 Toward the close of the second week, the mesenchymal spaces enlarge 

 and fuse with each other. There is thus formed a network of inter- 

 communicating spaces which invest and communicate with invading 

 capillaries from the first two or three post-iliac branches of the post- 

 cardinals. 



By the middle of the third week of development, the dorsolateral 

 branches of the postcardinal veins have fused at their distal ends to 



