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THE AMERICAN NATURALIST [Vol. XLIX 



agreement (cf. Ludwig, 1897, and Ritter and Crocker, 

 1900), that in some cases, if not in all, "this disparity in 

 size is due to the regeneration of halves of automatically 

 bisected animals." My observations fully confirm this. 

 I have witnessed, as did Ludwig, several cases of spon- 



of one or more rays may at any time be induced by holding 

 or injuring one or several rays, or by the stimulation of a 

 ray with dilute acid applied with a pipette. The autotomy 

 of a single ray takes place very much as described by 

 King (1898) for Asterias vulgaris; the existence of a 

 "breaking joint" in the region of the fifth ambulacral 



