LYMPHATICS IN FROG LARVAE 



67 



union of the two dorsal aortae in a single abdominal trunk. 

 At this point the subvertebral trunks pass outward and dorsal- 

 ward to end in the 'posterior collecting ducts' of the lymph 

 hearts. A collateral lymphatic runs along the outer border of 

 the mesonephros, on each side, connecting medially with the 

 subvertebral trunks through a plexus dorsal to the gland, and 

 also laterally with the 'lateral body lymphatics' through seg- 

 mental vessels. 



DNSlAO 

 INT JUGi- V 



B C 



Fig. B A reproduction of Hoyer's injection of the internal visceral lymphatics 

 in the abdomen of a 25-mm. larva of R. temporaria. He indicates the following 

 details: LH, lymph heart; Ts, subvertebral trunk; Tl, lateral body trunk; Lc, 

 collateral lymphatic. (A reduced copy of Hoyer's fig. 19 in memoir of 1934.) 



Fig. C An illustration of the anterior visceral lymphatics (cephalic) of an 

 18-mm. larva of R. palustris, with the deep pharyngeal lymphatic (DIM'HGL.L.) 

 uniting with the anterior collecting duct (ANT.OOL.L.). Other structures are 

 indicated as follows: anterior lymph heart, ANT.L.HT., immediately dorsal to 

 the pronephros, PRON ; the posterior collecting duct is seen over the surface of 

 the heart. Dorsal aorta, DRSL.AO.; internal jugular vein, INT.JUGL.V. ; sub- 

 ocular lymphatic, SO.L. ; etc. The drawing is by Miss Krause from a double 

 injection; the lymphatics blue, blood vessels black. 



Posteriorly, at the base of the tail, all of the long trunks 

 unite in a plexus, which receives the ventral caudal lymphatic. 

 Anteriorly, small branches of the subvertebral trunks spread 

 between the two aortae in a plexus which connects with a plexi- 

 form ring of visceral lymphatics encircling the oesophagus. 



The subvertebral trunks evidently represent the thoracic 

 ducts of higher forms, as Hover ( '34) suggests. 



