MR. F. D. DYSTER ON PHORONIS HIPPOCREPIA. 253 
which for convenience may be called the artery. Along it the blood rushes upwards in a 
powerful stream, until it arrives at the base of the lophophore, where it bifurcates, giving 
a branch to each of the rami. These branches open into sinuses which extend all round 
the lophophore ; and a twig is given off to each tentacle. The blood pursues its course to 
the extremity of the tentacles, which are provided with contractile vessels, tied down on 
one side, free on the other. The progress of the blood is not uniform in the tentacles, as 
it will be frequently seen to be ascending one while it is descending another, and some- 
times the stream may be observed to recede from one tentacle and then fill the adjoining 
one instead of falling back into the general circulation. ‘Two venous trunks open from 
the sinuses above and behind the arterial branches, and then proceed downwards, half 
encircling the cesophagus, till they unite in a large vessel on its neural surface. The 
blood moves by pulsations in the artery, at the rate of from twelve to fifteen beats a minute, 
the vessel contracting on it as it passes upwards, and remaining empty in the intervals 
between the beats. The returning stream through the neural vessel is perfectly conti- 
nuous. In the course of the body the neural and hæmal vessels are connected by nume- 
rous capillary loops; and when the upper portion of the body is removed, the circulation is 
quickly re-established through the loops nearest the point of scission, and carried on as 
powerfully as before. 
The blood consists of a colourless liquor sanguinis, densely charged with red globules 
of irregular shape and size, varying from circular to elliptical, flattened and somewhat 
concave on one side. In length they vary from 5355th to røygth of an inch. The thick- 
ness is about zg5gth. All are provided with one, many with two nuclei of granular ap- 
pearance, about 5545s5th of an inch in diameter. They are exceedingly flexible, and turn 
about, double, elongate, and flatten when pressed for room by meeting other globules in 
the capillaries, exactly as globules of human blood do when seen coursing about under 
thin glass. There are no colourless corpuscles; and very careful watching detected no 
- Ameba-like movements. They coagulate in masses which appear homogeneous, the nuclei 
only remaining visible. Treated with acetic acid, the cell-lining contracts, and all the 
globules assume a perfectly spherical form. There seems no ground for supposing that 
any special heart-like organ is concerned in the circulation of Phoronis. At whatever portion 
of the body section was made, after the shock of separation was recovered from, the pulsa- 
tions of the hæmal vessel were renewed with the same vigour as before; and this occurred 
in the posterior extremity of one individual which was dug out to nearly its full extent. 
The ovary lies below the stomach, and is, I believe, single. It is a long cylindrical 
vessel, pyriform at its base, perfectly transparent, and scarcely distinguishable except by 
its contained eggs, which appear to be attached to the inner surface. The ova are slightly 
elliptic, granular, about røsgth of an inch in diameter: the individuals of which the 
-ovaries were examined were all young; and there was no difference in the size or wind 
lopment of the ova. No specimen was observed without an ovary; bat cin conly eed 
spermatozoa were found. The body of these measured from rærsth to rørsth of an inch, 
with a filiform tail of equal length. 
The ova when deposited are white, 
not ciliated. The. oviduct lies above the rectum, on 
spherical, about shoth of an inch in diameter, and 
the hemal surface, immediately 
212 
