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THE AMERICAN NATURALIST [Vol. XLVIII 



the feeding reactions, as Pearse has pointed out, indicate 

 a bilateral type. The single genital gland is median in 

 position; the genital duct and the stone canal are in the 

 median dorsal mesentery ; a part of the intestine and the 

 stomach are supported by the same structure. The respi- 

 ratory apparatus is also a bilateral structure, one branch 

 arising from each side of the cloaca. 



viduals involve structures of the radial type. Fig. 1 is a 

 diagrammatic drawing of a dissection to show the general 



