1897-98.] Dr Masterman on Ar chimeric Segmentation. 285 
the trunk-cavity.* It is probable that these cavities are homo- 
logous in the groups mentioned, and the suggestion is here made 
that they are further homologous to the archimeric segments of 
Fig. 6. — Diagrammatic sagittal section through Phoronis , 
Erachiopoda, and Ectoprocta. 
the typical Ar chi-coelomata. Whether these three groups are 
phyletically related more recently than by means of the arclii- 
coelomate pelagic ancestor is at least open to doubt. As regards 
the other features of the Ar chi-coelomata, the Brachiopoda have 
* Lehrluch, cl. v. Entwickel, d. Wirb. tin., p. 1251. 
