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THE AMERICAN NATURALIST [Vol. XL VIII 



were attached only a short way back, much in front of 

 the position of attachment of the full-sized retractors. 

 In another animal killed when a day or so older, the same 

 conditions held with reference to esophagus, stomach 

 and intestine. At least three of the radial canals belong- 

 ing to the water vascular system had branched and con- 

 nected at their anterior ends in such a manner as to 

 form a part of a new ring canal (cf. Fig. 4). I was un- 

 able to find the rest of the ring-canal and perhaps it was 

 not yet complete. 



Thyone F, which was killed twelve days after eviscera- 

 tion, showed minute calcareous plates which formed a 

 very small esophageal ring not more than one millimeter 

 in diameter. The esophagus continued posteriorly in the 

 form of a small tube, the stomach-intestine, which was 

 suspended in the dorsal mesentery. This new digestive 

 tube was about 0.5 millimeter in diameter and contained 

 small, colored, movable particles that could be seen with 

 the unaided eye. The ring canal was completely formed. 



Another specimen, Thyone 0, died at the end of four- 



