65 
1895 - 96 .] Mr Arthur T. Masterman on Phoronis. 
the approximation and fusion of post-oral tentacles), all situated in 
front of the true mouth, we at least should not expect to find 
organs fulfilling similar functions in the endodermal area behind 
the mouth. 
Although, therefore, there are no notochord nor gill-slits in the 
adult Phoronis , yet we can find analogous organs and therein — 
reasons for the forestalling or replacement of these two structures. 
A few words with reference to the Table of Comparison : It will 
be seen that Phoronis offers various points of resemblance to each 
usually acknowledged member of the group, and thereby lends sup- 
port to the constitution of the group as such. 
We may note that, in sedentary habit, pre-oral lobe, and collar- 
region, Phoronis most nearly agrees with Ceplialodiscus and Rhabdo- 
pleura ; and in the shape and structure of the trunk, including 
vascular system, it more nearly resembles Balanoglossus. 
In comparing these two forms, I would amplify Wilson’s sug- 
gestion ; and by separating the anal half of the trunk from the 
anterior half, in fact, straightening out the trunk, would eliminate 
a point of dissimilarity which is due to a secondary adaptation on 
the part of the tubicolous Phoronis. ( N.B . — It is well to note that 
a similar mode of comparison' must be held valid by those who 
contend for a phyletic connection between Balanoglossus and the 
other Hemichordata.) 
Diagram 1 may be taken to represent a transverse section through 
the trunk region of Phoronis, the rectum being detached from its 
secondary connection with the lateral mesentery, and the ventral 
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