72 HENRY MCELDEBEY KNOWER 



which meet over the heart in the strong arching reception 

 chamber of the older larva. 



2. The establishment of the anterior accessory dorsal lymph 

 system, shown in Hoyer's figures, over the brain and sense 

 organs, has now been traced in these injections as an exten- 

 sion from the primary dorsal heart plexus (fig. 27 and the 

 later fig. 31). The afferent ducts enter the reception chamber 

 over the heart. 



3. One of the most conspicuous features of the late larvae 

 of R. temporaria (Hoyer, '05) is the diversion of almost all 

 of the lymph from posterior structures to the right and left 

 at the base of the tail into large lateral trunks. Only a deli- 

 cate, irregular plexus is left on the dorsal surface of cord and 

 hind-brain, with loss of the median dorsal lymphatic, which 

 has been an important direct channel from the posterior 

 tissues to the anterior plexus over the heart in the early 

 period. 



Unlike R. temporaria, the other frogs exhibit no such ex- 

 treme modifications of the primary arrangements, the main 

 dorsal duct remaining patent and maintaining practically the 

 same relations throughout the entire series of stages, as in 

 the. 18-mm. R. palustris larva (fig. 31), even as late as meta- 

 morphosis. 



4. The large 'lateral body lymphatics' of late stages 

 (Hoyer, '05, 26 mm.) have been shown in these injections to 

 be inaugurated in the early period, by diversion of lymph 

 laterally from the dorsal lymphatics, the posterior lateral 

 connectives becoming constantly stronger. 



In addition, in late larvae the lateral body lymph trunks 

 are augmented still further by fusion of elements of the ven- 

 tral lymph plexus with them. 



5. The description of the internal visceral system of the 

 18-mm. R. palustris larva confirms Hoyer's account, adding 

 only certain cephalic lymph vessels. 



6. The account of late features has been restricted, in this 

 paper, to those which appear to furnish a better understand- 

 ing of the well-known injections of Hoyer's late larval stage; 

 later developments having been outlined by Ranvier (1896), 



