^^HS REGENERATION OF ARMS IN BRITTLE-STAR. I 5 



urements taken 33 days and 46 days after the operation. Thus in 

 the 3 3 -day measurement for Series I. and II. 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 iQ-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 

 1 8 mm. The medium sized individuals tints have the maximum 

 rate of regeneration. 



2. More striking still is the very constant difference between 

 the average of Series I. and II. as compared with Series III. and 

 IV. This shows a very decided advantage in favor of the ani- 

 mals with the greater number of removed arms. The difference 

 is evident in the upper curves of the figure 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 1 2-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. -II. and of 3.45 

 mm. for Series III. -IV., an advantage of 1.37 mm. or 66 per 

 cent, in favor of the latter. Likewise at a diameter of 14 mm. 

 (where the Series I.-II. has its maximum regeneration) we get 

 2.37 mm. for Series I. II. and 2.77 mm. for Series III. -IV., an 

 advantage of .4mm. or 17 per cent, in favor of Series III. IV. In a 

 similar manner in the curves obtained from the 46-day measure- 

 ments we get at a 12 -mm. disk diameter a regenerated length of 

 2.46 mm. for Series I.-II. and 5.42 mm. for Series III. -IV., 

 and at a 15 -mm. diameter 3.14 mm. for Series I.-II. and 3.72 

 mm. for Series 1 1 1. -IV. which represents an advantage for the 

 group with the greater number of removed arms of respectively 

 2.96 mm. (= 1 20 per cent.) and .58 mm. ( = 18 per cent.) for 

 the two points named. 



We must therefore conclude that when more than one arm is 

 removed the regenerative energy as expressed in the replacement 

 of the lost arms is greatly increased. Not only is the total re- 

 generative energy greater in this case but the energy expressed 

 in each arm is greater than the total energy when only one is 

 removed. 



