THE DEVELOPMENT OF THE POSTERIOR LYMPH HEARTS 
OF THE LOGGERHEAD TURTLE. 
PRx^NK A. STROMSTEN. 
Recently, in a paper read before the American Society of Zoologists, 
central section, the writer presented some observations which indicated 
that the lymphatic system of turtles has an origin more or less inde- 
pendent of the venous' system. Since then later investigations on the 
Chelonian lymphatics confirm and strengthen this view. Even in the de- 
velopment of the posterior lymph hearts, which are generally conceded 
to be direct derivatives from early redundant embryonic veins, we find 
that the process is initiated, at least, by the dilation and confluence of 
mesenchymal spaces. 
The posterior lymph hearts are a pair of elliptical or ovoid, pulsating 
organs found just below the carapace in the post-iliac regions of the tur- 
tle, one on each side of the body. They drain the lymph cavities and 
spaces of the posterior part of the body, and open into the tributaries of 
the posterior renal advehent veins. 
The development of the posterior lymph hearts is initiated by the 
vacuolation of the subcutaneous mesenchymal tissue of the post-iliac re- 
gion. outside of the muscle plates. Toward the close of the second week of 
development the spongy tissue thus formed is invaded by capillaries 
from the first two caudal branches of the postcardinal veins. The con- 
fluence of the mesenchymal spaces with each other and with the invading 
capillaries forms a spongy network of minute channels which collects the 
lymph from the rapidly growing limbs and tail, and conveys it to the 
postcardinal veins. Near the middle of the third week, a longitudinal 
anastomosis of the segmental branches of the postcardinal veins takes 
place outside of the muscle plates. This forms a large vein on each side 
of the body which continues forward in the adult, to form the main 
branch of the posterior renal advehent vein, and backward into the tail 
as the lateral coccygeal vein. This pair of newly-formed veins now re- 
ceives all of the lymph from the anlagen of the lymph hearts. The pro- 
cess of the dilation and confluence of the mesenchymal spaces with each 
other and with the capillaries continues with increasing rapidity 
throughout the latter part of the third week, forming a number of large 
