136 Proceedings of Royal Society of Edinburgh. [sess. 
It has of late become the custom, especially since the appearance 
of Professor Spengel’s monograph on Balanoglossus and by certain 
German writers, to question the claims of this genus to vertebrate 
affinities. I would therefore point out that its close relationship 
to Phoronis , advocated in this and a former paper, is quite 
independent of the validity of these claims, though of course the 
right to consider Plioronis in any way connected with the vertebrate 
tree stands or falls with that of Balanoglossus. 
REFERENCES IN WOODCUTS. 
C.C., 
collar cavity. 
car, 
coelome. 
d., 
diverticulum or pouch. 
d.b.v., 
dorsal blood-vessel. 
ect.. 
ectoderm. 
gh, 
pre-oral gland. 
i-, 
intestine. 
I.C.C., 
left collar cavity. 
l.t.C.f 
left trunk cavity 
nc., 
notochord. 
oes., 
oesophagus. 
p.c., 
pre-oral body cavity. 
p.a.r., 
peri-anal ring. 
r.c.c , 
right collar cavity. 
r.t.c., 
right trunk cavity. 
st., 
stomach. 
t., 
tentacle. 
he., 
trunk cavity 
v.b.v., 
ventral blood-vessel 
