ENTOMOSTRACA OF MINNESOTA. 159 
favoring the impression that there is here a veritable opening. The 
outflowing blood stream is bounded at first by the membrane above 
mentioned, which is farther on reflexed onto the shell and intestine so 
that the streams in the head flowing just under the shell are separated 
from the deep dorsal stream flowing from the heart.* This main cur- 
rent passes to the region of the eye between the horns of the cceca of 
the alimentary canal, and thence beneath the stomach, and here 
divides, part becoming external and a deeper part passing under the 
intestine, thence in front of the heart, flows into the deep sinus which, 
as before said, passes beneath this organ. Other portions of the 
returning stream flow around the angle of the union of the head and 
body and constitute a stream just above the feet in which the current 
flows vigorously. 
Yet other portions flow into the region of the shell-gland and are 
united with blood which here passes through the numerous sinuses 
described by Claus (’75) as surrounding this organ, and thence flows 
into the abdomen, uniting with the other two streams. A part also 
of the current in the head flows into the antenne where it follows a 
deep course through the basal joint in which the corpuscles may be 
seen to emerge to the surface from two points where are spaces be- 
tween the powerful muscles, the first being near the base and the sec- 
ond near the extremity of this joint, and then to return and join the 
superficial current. 
The corpuscles appear to enter the rami very rarely if at all. That 
part of the superficial stream which reaches the interior of the peri- 
cardial chamber passes between the muscles of antennz and jaws, and 
seems to find its way into the great current beneath the heart, though 
I have also thought to have seen it flow directly into the pericardial 
space as the lateral superficial streams do. That part of the super- 
ficial stream which reaches the posterior margin of the shell returns 
through a canal formed by the walls of the shell and the brood-space, 
between the ‘‘stutzbalken”’ of which the blood corpuscles can be seen 
to glide more rapidly than in the free lateral spaces. ' 
Lastly, it only remains to follow the fortune of the strong stream 
flowing along the neutral surface of the abdomen. The strong current 
flowing beneath the heart enters a broad sinus which lies over the in- 
testine and extends for over a third of its length, where its walls unite 
with the surface of the intestine above and thus open downward on 
either side. 
The stream thus directed flows toward the openings of the base of 
the feet. The structure of the branchiz has not yet been clearly de- 
* In Pasithea rectirostris this septum is easily seen as a swaying membrane, which near the eye is 
reflexed to the top of the shell. 
