68 DEVELOPMENT OF LYMPHATIC SYSTEM, FISHES 



of his investigation is that he was able to demonstrate that 

 the periaortic lymph channel in Chelydra serpentina arises in 

 the mesenchyme in an area entirely free of veins. 



Stromsten's investigations ('10, '11, '12) on the development of 

 the lymphatic system in reptiles (chelonia) have led him to con- 

 clude that the lymphatics are formed by a concrescence of inde- 

 pendent and discontinuous lymph spaces and that lymphatic 

 endothelium is formed in situ from mesenchymal cells. His ob- 

 servations were based largely upon a study of injected embryos, 

 and showed that the injecta did not reach the independent an- 

 lagen of the lymphatics, prior to their concrescence with one 

 another to form a system of continuous lumina which had estab- 

 lished a communication with the veins. 



Fedorowicz ('13) and more recently Kampmeier ('15), have 

 shown that the continuous lumina of certain lymphatics are 

 formed in the amphibia (anura) by the concrescence of originally 

 independent and discontinuous lumina. They conclude, how- 

 ever, that the endothelial walls of these lumina have been de- 

 rived from the endothelium of the veins. E. R. Clark ('lib) 

 regards the lumina of the developing lymphatics in amphibia 

 (in tail of larval amphibia) as always continuous and capable of 

 injection, while Fedorowicz and Kampmeier describe them as 

 discontinuous at the start. 



In the preceding pages the writer has demonstrated the pres- 

 ence of discontinuous and independent lymph vesicles in the 

 trout embryo, which cannot be injected from other lymphatic 

 anlagen or from the veins. Many of these vesicles arise in the 

 mesenchyme remote from the veins, and no connection can be 

 observed between their endothelium and that of the veins or that 

 of any other lymphatic anlagen. One of these independent 

 lymph vesicles, the subocular lymph sac, can actually be ob- 

 served in the living trout embryo. On account of the relatively 

 large size of this vesicle it has proved a most favorable object 

 for experimentation and for study in sections, not only in proof 

 of the fact that it arises independently of the veins, but also 

 that its endothelium is of mesenchymal origin. 



