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DEVELOPMENT OF LYMPHATICS IN ANURA 85 
reconstruction exhibits a number of other features. The jugular 
lymphatie (lym. jug.) by growth cephalad and the temporal divi- 
sion of the primary maxillary lymph sinus (temp. sv. max. prim.) 
by growth caudad (figs. 30, 34, and 35) have met and become 
continuous. Further, as shown in figure 34, the jugular and the 
lateral-line (lym. lat.) lymphatics, united from the beginning, 
develop prominent ventral branches lateral to the pronephros. 
The other tributaries, extending dorsally and showing a meta- 
meric tendency, unquestionably represent the distal portions of 
the intersegmental vessels from which the jugular lymphatic was 
derived. Finally, the minute connection (starred) between this 
plexiform duct and the pronephric sinusoids may be noted, which 
has managed to persist until this time. In a later stage (10-mm. 
embryo) the jugular, in common with the lateral-line lymphatic, 
has reunited with the lymph heart, and farther forward the junc- 
tion with the temporal division of the primary maxillary sinus 
has expanded (fig. 35). 
A few words respecting the venous circulation of the region 
under consideration will explain certain difficulties. Since the 
anterior intersegmental veins function as haemal conduits before 
their transformation into the plexus of the jugular lymphatic, as 
soon as their complete separation from the cardinal venous trunk 
is accomplished, the region of the myotomes which they drained 
would be left without a blood vascular return, but for the develop- 
ment of secondary channels from the cardinal veins. Accord- 
ingly, such tributaries are laid down at this time, but they are 
situated chiefly on the inner suface of the myotomes and accom- 
pany the spinal nerves and ganglia; here, besides receiving 
branches from the myotomes, they communicate broadly with 
similar channels from the aorta. In order not to complicate the 
reconstruction more than was necessary, the entire medial blood 
vascular plexus, except the main cardinal tributaries, was omit- 
ted. Besides these medial segmental tributaries, two or three 
lateral ones develop (figs. 34 and 35) in proximity to the lymph 
heart and are closely pressed against the outer side of the myo- 
tomes. At a later period, these venules anastomose, become 
larger, and combine to form the definitive anterior vertebral vein 
and its branches (fig. 35). 
