1895-96.] Mr Arthur T. Masterman on Phoronis. 
59 
Preliminary Note on the Structure and Affinities of 
Phoronis. By Arthur T. Masterman, B.A. (Cant.), 
Assistant Professor and Lecturer in Zoology at the University 
of St Andrews. 
(Read March 16, 1896.) 
In spite of the great amount of attention which has been 
bestowed upon this group by many workers, it must still be said 
that our knowledge of its systematic position is very meagre and 
uncertain, and that there are points in its anatomy which require 
elucidation. Through the kindness of Professor MTntosh I have 
been enabled to examine some specimens of P. australis , and also a 
Phoronis , which appears to be a new species. I reserve a detailed 
account of my results for later publication, and here only refer 
very briefly to leading points. I may mention that Professor 
MTntosh has also allowed me the inspection of his serial sections 
of P. buskii. MPntosh, and after a careful comparison I have 
not the slightest doubt that this is a distinct species from 
P. australis — it has been usual to regard the distinction between 
these two forms as not of specific value. 
Divisions of the Body. — It is usual, in describing the structure of 
Phoronis , to refer to two different parts of the body which lie before 
and behind the septum respectively. I propose, for reasons shown 
later, to emphasise the division of the body into — (1) The epistome, 
lying dorsally to the mouth, and having very definite, though some- 
what involved, relationship to the next part ; (2) the tentacular 
region, which I prefer to call the collar, consisting of a ring round 
the mouth region, the oral part being produced into two arms or pro- 
cesses which bear tentacles and are coiled, and the aboral end being 
limited superficially by the nerve ring and fundamentally by the 
so-called septum ; (3) the trunk, including all the region behind 
the septum. 
These three divisions are not mere conveniences of description, 
but are definite segments, having body-cavities separated from each 
other by mesenteries, and differing in form and function amongst 
themselves. 
The tentacles, as is well known, are arranged upon the lophophore 
