322 SERGIUS MORGULIS 



method of studying and of the difference of the animals experi- 

 mented upon (anneUd and amphibian), the general conclusions 

 drawn from both investigations are practically the same, except 

 perhaps on some special points. 



My investigation of the energy of regeneration of the tail in the 

 polychaet Podarke obscura, based upon the degree of differentia- 

 tion as determined by the number of regenerated segments, led 

 to establishing four distinct, though not sharply defined, stages 

 in the process of posterior regeneration. The first stage, during 

 which the wound closes over but the proliferation of the new organ 

 has not yet begun, is of very short duration, the length of time 

 depending upon the individual and also upon the level of the cut. 

 The second stage is marked by a very rapid formation of new seg- 

 ments; the third stage, during which new segments are still formed 

 at a high rate, is nevertheless characterized by a sudden fall in the 

 regenerative energy. These stages, two and three, extend over a 

 period of about two weeks; the ultimate size of the regenerating tail 

 attained at the completion of the process of regeneration practi- 

 cally depends entirely upon the progress made during this period. 

 The fourth and last stage is one of slow but continuous decline of 

 the regenerative energy until the zero point has been reached. 

 This succession of stages in the regeneration of the tail is repre- 

 sented by a curve, fig. 1, constructed according to the data con- 

 tained in tables 2 and 3 in the first paper of these contributions 

 to the physiology of regeneration (Morguhs '09). 



Miss Durbin ('09), experimenting on tadpoles of Rana clamitans 

 (Latreille), found that the new growth of the tail presents four 

 definite stages, essentially like those outlined above. The corre- 

 spondence of her results with those obtained on Podarke, apart 

 from the weight it lends to the conclusions, is also important 

 as indicating that either the degree of differentiation or the 

 amount of growth of the new organ may be equally relied upon 

 in studying the nature of the regenerative process. 



Below I reproduce one of Miss Durbin's curves (fig. 2) showing 

 the successive modulations of the intensity of tail regeneration in 

 tadpoles, in order to emphasise its close similarity to the curve of 

 tail regeneration in the worm (fig. 1). This curve was plotted on 



