THE ANATOMY OF PHORONIS AUSTRALIS. 145 
on the post-metamorphic condition of Actinotrocha, as a 
young Sipunculus. 
Kowalevsky (15) was of opinion that Phoronis belonged 
either to the Gephyrea or to the Polyzoa. 
Caldwell (4) points out the relations of Phoronis, so far as 
regards the arrangement of organs, to the Brachiopoda, and to 
- the Polyzoa, and concludes that Sipunculus belongs to the 
same type of form. 
Lankester (17) places Phoronis as the only genus in a 
section Vermiformia, of the class Polyzoa, and points out 
its relations both to Sipunculus and Eupolyzoa. 
We have therefore to consider the affinity of Phoronis to— 
(a) the Brachiopoda. 
(0) the Polyzoa. 
(c) the Sipunculids. 
a. The Relation of Phoronis to Brachiopoda. 
Caldwell (4) draws up a series of characters in which he 
considers these two types to resemble one another. Many of 
these have been controverted by Shipley (24) and others. 
According to the investigations of Shipley, no remnant 
of the pre-oral lobe persists in the Brachiopoda, so that 
there is no representative in them of the epistome of Pho- 
ronis, unless the “lip” which passes along the base of the 
tentacle and overhangs the lophophoral groove represents 
this structure. There are four and not three “ segments” 
in the Brachiopod larva. Moreover, the evagination in 
Actinotrocha appears to me to be totally different from what 
happens in the Brachiopod larva, as this does not involve the 
alimentary tract, and does not alter the long axis of the body. 
In his division of the body of Actinotrocha into three “ seg- 
ments,” Caldwell seems to have chosen them rather arbitrarily. 
He writes (4, p. 381): “ The ‘segments’ of Brachiopoda are 
represented in Phoronis by the three divisions of the larva: 
1, Pre-oral lobe, as far back as the septum ; 2. The rest of the 
7 « Polyzoa,” ‘ Ene. Brit.’ 
* “Structure and Development of Argiope,” ‘ Mith. Zool. St. Neap.,’ 1883. 
