382 



Mr. W. H. Caldwell. On the 



[Dec. 7, 



Brachiopoda are thus fixed by their ventral surface. 

 The dorsal surface is indicated by the epistome, and the line 

 between mouth and anus (when present). 

 Both valves of the shell are ventral. 



Phoronis and Polyzoa. 



With regard to the Polyzoa, the evidence owing to the simplifica- 

 tion which has taken place in their structure is not obtainable in the 

 same quantity. I regard it, however, as probable that the epistome 

 of Endoproct and Hippocrepian Polyzoa and the " foot " (Ray 

 Lankester) in Rhabdopleura represent the prseoral lobe. 



The dorsal surface in Polyzoa is indicated as in Phoronis by the 

 line between mouth and anus. If Phoronis, Brachiopoda, and Polyzoa 

 have had segmented ancestors no trace of such remains in their 

 ontogeny. 



The discussion of the various views at present held on the Polyzoa 

 and Brachiopoda must be deferred to my fuller paper. 



So far as the facts of development and structure of Sipunculus and 

 Phascolosoma are known, I see nothing to show that these forms are 

 not referable to the same type of body structure as Phoronis, Brachio- 

 poda, and Polyzoa. On the other hand, it seems quite possible that 

 they may be further stages in degeneration from forms like Echiurus, 

 which, after the researches of Hatschek, seem to be degenerated 

 Chastopoda. 



