Compensatory Regulation. I^ 



III and 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 and II has its maximum regeneration) we get 2.37 mm. for Series 

 I and II and 2.77 mm. for Series III and IV, an advantage of 

 .4 mm. or 17 per cent in favor of Series III and IV. In a similar 

 manner in the curves obtained from the 46-day measurements we 

 get at a 12 mm. disk diameter a regenerated length of 2.46 mm. 

 for Series I and II and 5.42 mm. for Series III and IV, and at a 

 15 mm. diameter 3.14 mm. for Series I and II and 3.72 mm. for 

 Series III and IV, which represents an advantage for the group 

 with the greater number of removed arms of respectively 2.96 mm. 

 (= 120 per cent) and .58 mm. ( = 18 per cent) for the two points 

 named. 



The difference between Series I and Series IV as represented 

 in Fig. 2 is still greater. The regenerated lengths are on the whole 

 at least twice as great in Series IV where four arms were removed 

 as m Series I where only one arm was removed. Thus at a disk 

 diameter of 8 mm. the regenerated length in Series I is 1.05 mm. 

 and the average regenerated length in Series IV is 2.3 mm., an 

 increase of 1.25 mm. or 119 per cent. For the same diameter at 

 33 days the respective values are 1.65 mm. and 4.4 mm., an 

 increase of 2.75 mm. or 167 per cent. At 46 days the correspond- 

 ing values are 2.0 mm. and 5.85 mm., an increase of 3.85 mm. or 

 192 per cent. 



Likewise at a 12 mm. disk diameter for 22 days the values are 

 .9 mm. and 2.1 mm., an advantage of 1.2 mm. or 133 per cent. 

 At 33 days the values for a 12 mm. disk diameter are 2.3 mm. and 

 4.2 mm., an advantage of 1.9 mm. or 83 per cent, and at 46 days 

 the corresponding values are 3.05 mm. and 6.5 mm., an advantage 

 of 3.45 mm. or 1 13 per cent. 



We may sum up the results on the rate of regeneration of the 

 arms of the brittle-star, Ophioglypha lacertosa, as follows: 



1. There is a definite relation between the size (/. e., age [ .?]) 

 of the animal and the rate of regeneration of its arms. The maxi- 

 mum rate is exhibited by individuals of medium size (with a disk 

 diameter of 12 to 15 mm.). Both the smaller and the larger ones 

 give a dihiinishing rate as we go away from this point. 



2. The greater the number of removed arms (excepting the 

 case where all are removed) the greater is the rate of regeneration 

 of each arm. 



