No. 424.] THE BLOOD FLOW IN LUMBRICUS. 323 
experiment the ventral and neural vessels were filled in front 
of, and empty behind, the clamps, indicating a backward flow 
in both. The parietals were filled both in front and behind 
the clamp. They were somewhat distended in front of the 
clamps, owing to increased pressure from the subneural in 
front of its clamp, while behind the clamps the parietals 
continued to collect some blood from the body wall and 
nephridia. 
In four worms the ventro-intestinals in several segments 
were cut in order to drain the intestine of blood in those seg- 
ments, and the dorsal was afterward clamped at both ends of 
the area in which the ventro-intestinals were cut. Between 
the clamps the dorsal decreased and the parietals were nor- 
mally full. In four other worms the same result was reached 
when the dorsal was clamped in one place and the dorso-intes- 
tinals were cut for several segments in front of the clamp. 
Since the dorsal retained some blood and the parietals kept up 
their normal fullness as long as the worm lived, while all other 
supply to the dorsal was cut off, it is impossible to reach any 
other conclusion from these experiments than that the parietals 
. bring blood to the dorsal. 
Pulsations of the parietal vessels are not always clearly visi- 
ble. In four worms in which the pulsations of the parietals 
were distinct and strong a large number of these vessels were 
carefully studied. The contraction of the parietals occurs 
opposite the front part of the pulse wave of the dorsal, z.e., 
while the dorsal is reaching its greatest fullness. The parie- 
tals fill just after the contraction of the dorsal, z.e., opposite 
the point of constriction of the dorsal behind the pulse wave. 
The filling of the parietals is sudden and the contraction slow. 
This, taken together with the order of the contractions, indi- 
cates that the contraction of the parietals helps to swell the 
dorsal just in front of the constriction which carries its pulse 
wave along, while the rapid filling of the parietals is due to 
the sudden closure of the parieto-dorsal openings by the con- 
traction wave of the dorsal. The results of all the experi- 
ments considered together strongly favor the conclusion that 
the parietals carry blood to the dorsal. 
