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anastomosing spaces, the veno-lympliatic channels. These channels ex- 
tend parallel with the veins and open into them at two or three points. 
At first the veno-lymphatic channels contain red blood cells and are 
indistingnishahle from the veins as regards size and general appearance. 
Later, however, they acquire rather dense walls which contain striated 
muscle fibres. The cardiac muscle fibres of the lymph hearts are derived 
from the adjacent muscle plates. The partitions between adjacent veno- 
lymphatic channels begin to .atrophy toward the beginning of the fourth 
week, so that by the end of the week we find a pair of large sacs with 
muscular walls, each with a single central cavity. 
Thus we see that the posterior lymph hearts of the loggerhead turtle 
are developed from embryonal capillaries which have been captured and 
modified by the dilated mesenchymal spaces' of the post-iliac regions of 
the body. 
