248 George S. Huntington and Charles F. W. McClure. 
blind diverticular extremity. When compared with the recon- 
struction of the left side (fig. 33) it appears possible that this 
diverticular extremity may have been derived from tributary 3. 
Such a condition might easily be brought about as the result of a 
fusion between the veno-lymyhatic components of tributaries 3 
and 4. Measurements of the two reconstructions seem to bear 
out this view. (See also 3VL, in fig. 47). 
The dorso-laterally situated veno-lymphatic complex of tribu- 
tary 4 (4VL) and its associated para-precardinal channel (para-pre- 
cardinal channel, VL) communicate at three points on _ the 
right side of this embryo with the main precardinal vein (at X, X’ 
and X”’, figs. 35 and 36). The most anterior point of communica- 
tion at X” (fig. 35) is not present on the left side of the embryo 
(fig. 33) unless, as intimated above, it may be represented by the 
precardino-veno-lymphatie confluence of tributary 3. The com- 
munications with the precardinal at X and_X’, however, are repre- 
sented on both sides of the embryo, as is evidenced by compara- 
tive measurements of the two sides. (Compare X and X’ in figs. 
33, 34 and 35). } 
On the right side of the embryo the communication with the 
precardinal at. X occurs dorso-medially and in common with a 
secondary somatic component of tributary 4 (49’, fig. 36), while on 
the left side of the embryo the communication with the precardi- 
nal at X occurs dorso-laterally and independently of a somatic 
branch (X, fig. 33). 
The same reverse conditions prevail regarding the point of 
communication with the precardinal at X’, since it occurs dorso- 
laterally on the right side (X’, fig. 835) and dorso-medially on the 
left (X’, fig. 34). 
The communication at X on both sides of the embryo probably 
represents the persistence of the primary union of tributary 4 with 
the precardinal (see series 109, X, fig. 28), while the communi- 
cation at X’ probably represents an instance in which the para- 
precardinal channel has not been completely separated along its 
entire extent from the precardinal vein. 
Caudally, the veno-lymphatic complex of tributary 4 and its 
associated para-precardinal channel enlarges and presents a multi- 
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