340 
^V1LUA^[ F. ALLEN. 
found in the turtle, and in line with the earlier work on the 
lymphatics, as illustrated by Budge and Sala, but at variance 
with a considerable recent Avork on the development of the 
lymphatic sacs in the higher Yertebrata by Miss Sabin, 
Huntington, McClure, Lewis, KnoAver, Hoyer, Baetjer, 
Barauski, and others, ay ho maintain that the lymph-sacs in 
mammals, birds, reptiles and amphibians have their origin 
directly from the larger veins, either as sprouts or fenestra- 
tions, or from their branches or capillaries. 
V. Development of the A^enteal AL:no-Lymphatic Teuxk. 
It is my intention in this paper only to take up the manner 
of formation of this trunk in so far as to isolate it from the 
caudal hearts, Avith Avhich it is A'ery closely associated. 
In a transA'erse section taken through the anterior end of 
the left embryonic caudal heart of a 20 mm. series, as, for 
example, Figs. 5 and 13, there Avill be seen some distance 
below the left caudal vein a conspicuous isolated cavity in the 
mesenchj^me (Lv.v. ,i)), containing seAmral red corpuscles. 
If no further examination of this ca\dty be made, it might 
easily be dispensed Avith as an isolated Amntral mesenchymal 
caAuty that Avould take part in the formation of the left 
caudal heart. If, liOAveAmr, this cavity is traced further 
ceplialad it Avill be found, as is shoAvn in reconstractiou 
(6, I. V. V. Q)), to be situated too far \mntrad to take any part 
in the construction of the left caudal heart, and in addition it 
can be followed under the embryonic lateral process of the 
median ventral cartilaginous bar to a point Avithin 30 microns 
of a Amrtical plane that passes through the point of bifur- 
cation of the caudal artery, Avhich of course is considerably 
cephalad of the limits obtained by the caudal heart. It Avill 
also be noted that this rather large cavity Avas formed by the 
union of tAVO or more smaller mesenchymal spaces. This 
large cavity I belieAm to be the first, or most anterior, of a 
series of mesenchymal cavities that Avill occur later and 
coalesce to form the posterior portion of the A'entral A^eno- 
