422 L. II. HYMAN. 



of injury relative to the mass of the regenerating piece or organism. 

 Some years ago under the leadership of Zeleny there was con- 

 siderable interest in this matter. A number of papers dealing 

 with this subject were published (Zeleny, '03, '050, '056, '07, 

 Ellis, '07). A general agreement was reached by the workers 

 in this field that any one part is replaced at a more rapid rate, 

 the greater the amount of tissue removed at the original opera- 

 tion. It is possible that this result also depends on metabolic 

 rate; for every wound is the locus of an increase in metabolic 

 rate and the greater the number of wounds and the smaller the 

 mass of tissue remaining the greater is the stimulation of respira- 

 tory metabolism not only at the wounds but also in the adjacent 

 uninjured parts. 



In general, then, it appears that the size of regenerated oral 

 or apical structures and the amount of tissue produced in a given 

 time are causally related to the metabolic rate of the regenerating 

 mass. 



When metabolic factors such as level, age, or wound stimu- 

 lation are not involved, the mass of the piece appears to have 

 little or no effect upon the amount of tissue regenerated in a given 

 time. Thus it is shown in this paper for Tubularia that pieces 

 differing considerably in length and hence total mass regenerate 

 oral hydranths of equal size in equal lengths of time. Because 

 of this lack of relation between mass and regeneration it can be 

 stated as a generalization that the smaller the original mass 

 (within certain limits of course) the greater relative to its mass 

 is the amount of tissue produced in a given time. Other data in 

 support of this statement will be found in many of the papers 

 already cited. 



It remains to consider a paper by Lund ('23) on regeneration 

 in Obelia, in which paper certain conclusions are stated which 

 seem to be at variance with those presented here. In the re- 

 generation of Obelia as previously noted by Billard ('04) a process 

 grows out from the cut surface and the hydranth differentiates 

 at the end of this outgrowth. Lund has studied the time 

 occupied by this growth process and the rate of elongation of the 

 outgrowth in a series of pieces cut in apico-basal sequence from 

 the main stem of colonies of Obelia. Lund finds as did Billard 



