138 WILLIAM BLAXLAND BENHAM. 
to detect any cells, but I think we may safely consider that 
all these, as well as the tentacular skeleton and that of the 
epistome, have really the same structure. 
The Vascular System.—The character which has struck 
all those observers, such as Strethill Wright (25), and Dyster 
(6), who have examined the living Phoronis, is the red colour 
of the vascular system. 
This consists of a closed system of vessels containing a 
colourless plasma, in which float round, nucleated, disc-like 
corpuscles, which are coloured red by hemoglobin as demon- 
strated by Lankester. These corpuscles, even in preparations 
stained in borax carmine, are readily distinguished from the 
ccelomic corpuscles, owing totheir yellowish tint. Moreover, they 
are rather more coarsely granular (fig. 21) than the latter. The 
system of blood-vessels was, by the above-named observers, ob- 
served to be contractile, and the course of the blood and arrange- 
ment of the vessels were pretty accurately described by them. 
There are two longitudinal trunks lying in the celom, 
running into one another at the proximal end of the body, but 
not elsewhere directly connected, though there is an indirect 
communication in the tentacles. 
One of these trunks, the afferent trunk (qf. in figs. 23, 24, 
31 and 33), lies in the rectal chamber in the middle line 
between oesophagus and rectum. Distally it divides into a 
right and left branch immediately below the septum, quite 
close to the oesophagus, and each branch then passes-through 
the septum. Each of these “ distributing vessels” passes 
along the corresponding half of the lophophore, and there- 
fore takes a spiral course. From these distributing 
vessels (dv., fig. 23) a very narrow vessel passes up each 
tentacle. Each of these tentacular vessels (¢v.) ends blindly at 
the tip of the tentacle. These were observed to be contractile 
by Dyster, who saw the flow of blood up some tentacular 
vessels, and down others. Hach tentacular vessel is connected 
at its base, not only with the above-mentioned distributing 
*5 « Description of Two New Tubicolous Animals,” ‘ Proc. Roy. Phys, 
Soe, Edin.,’ 1855, 
