THE EFFECT OF DEGREE OF INJURY, SUCCESSIVE 

 INJURY AND FUNCTIONAL ACTIVITY UPON RE- 

 GENERATION IN THE SCYPHOMEDUSAN, CAS- 

 SIOPEA XAMACHANA^ 



CHARLES ZELENY 



With Four Figurfs 



INTRODUCTION 



The present study is a part of a series of experiments whose 

 object is the investigation of some of the internal factors control- 

 hng regeneration in several representative forms. The factors 

 taken up in Cassiopea are the degree of injury, successive removal 

 of a part and rhythmical pulsation of the disk. It is found that 

 removal of six of the eight oral arms constitutes the most favorable 

 degree of injury for the regeneration of each arm, and that from 

 this optimum there is a decrease in both directions. The data for 

 successive injury show a greater rate of regeneration of the margin 

 of the disk after the second removal, than after the first. A com- 

 parison of the rate of regeneration of the margin in cases where 

 the disk was made to pulsate rhythmically with cases without 

 pulsation shows no advantage in favor of the pulsating ones, but 

 rather a retardation. 



' Contributions from the Zoological Laboratory of Indiana University. No. 92. 



I am indebted to the Carnegie Institution of Washington, for the privilege of working at their labora- 

 tory at Tortugas. To Dr. A. G. Mayer, the director, I am under obligation for many kindnesses and 

 especially for suggestions in connection with the work. 



The present paper is the fourth of a series dealing with the internal factors controlling the rate of 

 regeneration. The other three papers are: a A study of the rate of regeneration of the arms in the 

 brittle-star, Ophioglypha lacertosa. Biological Bulletin, vol. vi, no. i, December, li 903; 6 The relation 

 of the degree of injury to the rate of regeneration. Journal of 'Experimental Zoialogy, vol. ii, no. 3, 

 August, 1905; c Some internal factors connected with the regeneration of the chelae in the Gulf- weed 

 Crab, Portunus Sayi. In press. Carnegie Institution. 



The Journal of Experimental Zoology, vol. v, no. 2. 



