THE ANATOMY OF PHORONIS AUSTRALIS. 147 
in Polyzoa it has been suggested that it is the dorsal region 
which predominates (Barrois (2), Harmer (8, 9) ). If this view 
should prove correct, then the space then between mouth and 
anus would be dorsal in the former and ventral in the 
latter case, and the epistome which is the vestigial repre- 
sentative of the pre-oral lobe of the larva in Phoronis, would 
in Polyzoa correspond rather to the foot of Mollusca, or the 
‘ invaginated region of Actinotrocha. This orientation is, how- 
ever, quite hypothetical. If admitted it becomes useless to 
discuss any relationship between Phoronis and the Polyzoa. 
In the Phylactolcema the two arms of the horse-shoe-shaped 
lophophore are free and movable. In Phoronis, however, the 
lophophore is fixed throughout the whole of its extent to the 
body. In Rhabdopleura and Cephalodiscus alone, of 
the Polyzoa, is there, as in Phoronis, a skeleton in the 
tentacles. 
Again, the series of tentacles is incomplete dorsally in 
Phoronis, whilst this dorsal break is not present in Polyzoa, 
except in Rhabdopleura. 
In the Ectoprocta the bases of the tentacles are frequently 
united by a membrane in a way that has been compared to 
that of Phoronis, but, as I have shown above, this is due 
in the latter animal to the way in which the tentacular 
skeleton is formed, and there is no real “ membrane,” but 
direct fusion. 
The celom in Phoronis is subdivided (in a way unknown 
in Polyzoa), firstly, by a transverse septum of cartilage sepa~ 
rating the general body-cavity from the cavity of the epistome 
and tentacles. The former is again divided by longitudinal 
mesenteries of the same sort of tissue into various chambers. 
Unless the “funiculi” represent such mesenteries they are 
absent in Polyzoa; but no great stress can be laid on these 
points of difference since mesenteries are found in many 
distinct groups of animals, and may be either present or 
absent in closely allied forms. 
The pair of nephridia present in Phoronis may or may 
not be distinct from the nephridia of Loxosoma, which are 
