8 CHAELES F. W. McCLURE 



through the concrescence of independent and discontinuous 

 anlagen. See McClure, 1921, for an historical account of 

 the investigations bearing on this subject. 2 



A study of living trout embryos made by the writer 3 has 

 demonstrated that certain of these independent anlagen of 

 the lymphatic system, the subocular lymph sacs, receive 

 through their closed endothelial-lined walls lymph which 

 flows from the interstitial spaces in a centripetal direction, 

 and that the lymph received in these sacs is temporarily 

 retained by them until the sacs secondarily join the lateral 

 pharyngeal lymphatic (jugular), by which it is then trans- 

 ported to the venous circulation. Subocular lymph sacs were 

 observed also in the embryos of Amia and Lepidosteus. In 

 the embryos of ganoids, however, these sacs communicated 

 directly with the veins at a very early stage of development, 

 so that the lymph received in them was not retained, but was 

 directly transported to the venous circulation. What we find 

 to be the case in both trout and ganoids is that lymph from 

 the tissue spaces flows in a centripetal direction through the 

 endothelial-lined walls of blindly ending lymphatics, and that 

 in the case of the trout this lymph is temporarily retained 

 by closed and detached independent anlagen of the lymphatic 

 system, until the conditions are such that the centripetal flow 

 can be continued to the venous circulation. It can therefore 

 actually be demonstrated in the living trout embryos not only 

 that certain lymphatics end blindly, but also that certain of 

 the independent anlagen of the lymphatic system serve as 

 reservoirs for the reception and temporary retention of 

 lymph received from the interstitial spaces prior to the estab- 



MeClure, C. F. W. 1921 The endothelial problem. President's address: 

 read before the American Association of Anatomists in Philadelphia. Anat. Eec., 

 vol. 22. 



' McClure, C. F. W. 1915 The development of the lymphatic system in fishes 

 with especial reference to its development in the trout. Amer. Anat. Mem., no. 4. 



1915 On the provisional arrangement of the embryonic lym- 

 phatic system. An arrangement by means of which a centripetal lymph flow 

 toward the venous circulation is controlled in an orderly and uniform manner, 

 from the time lymph begins to collect in the intercellular spaces until it is for- 

 warded to the venous circulation. Anat. Kec., vol. 9. 



