14 Charles Zeleny. 



the average of the former group (one and two arms removed) and 

 the broken Hne the average of the latter group (three and four 

 arms removed). 



3. Data. 



The curves show very distinctly the correlation between the 

 rate of regeneration on the one hand and the size of the animal 

 and the number of removed arms on the other. 



1. Taking up first the size correlation and using Fig. 3 as our 

 basis of comparison, since it contains all the cases except those of 

 Series V and therefore gives a more uniform and complete curve, 

 we find that starting with the smaller individuals as we advance 

 toward the larger ones there is a general increase up to a maximum 

 at a diameter of 12 to 15 mm. This is most striking in the tw^o 

 later measurements, taken 33 days and 46 days after the operation. 

 Thus in the 33-day measurement for Series I and II (Fig. 3), the 

 regenerated length increases from 1.07 mm. for a disk diameter 

 of 7 mm. to a maximum of 2.37 mm. for a disk diameter of 14 mm., 

 and then goes down to .21 mm. for a 19 mm. diameter. Also for 

 the Series III and IV at the same time the length increases from 

 2.04 mm. at a diameter of 7 mm. to a maximum of 3.45 mm. at a 

 12 mm. diameter, and down again to 1.36 mm. at a diameter of 

 18 mm. The medium-sized individuals thus have the maximum 

 rate of regeneration} 



2. More striking still is the very constant difference between 

 the regenerated lengths for Series I and those for Series IV in 

 Fig. 2, and between the lengths for the combination of Series I 

 and II and those for the combination of Series III and IV in Fig. 

 3. This shows a very decided advantage m favor of the animals 

 with the greater number of removed arms. The difference is 

 evident in the upper curves of Fig. 3 from measurements taken 

 22 days after the operation, but becomes more striking in the 33- 

 day and 46-day curves. For example, in the 33-day curve for a 

 12 mm. diameter (the diameter at which we have the maximum 

 rate of regeneration of Series III and IV) we get a regenerated 

 length of 2.08 mm. for Series I and II, and of 3.45 mm. for Series 



^ Dr. Hans Przibram has called my'attention to the fact that the specific rate of regeneration of the 

 arms, ;'. e., the amount of regeneration per unit of disk diameter as obtained from my data, does 

 not show this increase from the smallest up to the medium-sized individuals, but gives a fairly constant 

 figure up to 12 or 14 mm. The higher diameters then decline rapidly toward a minimum. 



